Major spoilers. This is not an attack on the film. It is a mock trial: we temporarily apply Japanese criminal-law ideas to the story and let the prosecutor, defense, court, and characters work through the questions.[1][2]
1. The trial stops immediately at “Are mermaids legally people?”
Clerk: “All rise.”
Judge: “We will begin the Mermaid Island case.”
Chiikawa: “Wah…”
Hachiware: “It’ll be okay!”
Usagi: “Yaha.”
Momonga: “Finish quickly!”
Judge: “Before homicide, one question. Are mermaids and Siren ‘persons’ under criminal law?”
Hachiware: “We’re starting there!?”
Prosecutor: “Article 199 punishes killing a person. The statute was not written with mermaids, Siren, or chimeras in mind.”[3]
Hachiware: “So if they aren’t legal people, anyone can kill them?”
Judge: “No. Being protected by law, being a ‘person’ for homicide, and being capable of criminal responsibility are different questions.”
Hachiware: “How?”
Judge: “A baby deserves full protection, but we do not punish a baby like an adult offender.”
Hachiware: “Oh. Rights and responsibility are different.”
Prosecutor: “For a chimera, we would ask whether it understands what it is doing, understands harm, and can control itself. Siren speaks, remembers, searches for a culprit, makes demands, and changes plans. That looks more like an accountable intelligent agent than a purely instinctive animal.”
Defense: “But a court also cannot simply say, ‘It is smart, so today we expand the criminal statute.’”
Judge: “Correct. For this mock trial only, we will assume highly communicative, choosing beings count as persons. That is not a claim about actual Japanese law.”
Chiikawa: “Eh…?”
2. Once the facts are connected, everyone has a reason
Prosecutor: “Hitoha and Futaba were fishing. An accident connected to Siren’s actions left Futaba near death. Hitoha killed a mermaid and fed its flesh to Futaba. Futaba survived and became effectively immortal; Hitoha later ate the flesh too.”[4]
Prosecutor: “Siren lost a mermaid companion and searched for the culprit. When the culprit did not appear, Siren took and ate islanders who might have had nothing to do with the killing. The islanders then recruited outside fighters, and Chiikawa’s group entered without knowing the whole history.”[1][4]
Hachiware: “So this isn’t ‘a monster suddenly attacked innocent people’.”
Judge: “Right. Hitoha wanted to save a friend. Siren lost a friend. The islanders did not want to be eaten. Chiikawa’s group wanted to protect one another.”
Momonga: “Then everyone is innocent!”
Judge: “Having a reason is not the same as having permission.”
3. Kotake Seigikan’s legal-check video is the doorway, not the final judgment
Hachiware: “Why are we trying this case at all?”
Prosecutor: “On September 3, 2026, lawyer-comedian Kotake Seigikan published a legal-check video about the film. Reports highlight the 100× reward, fraud and advertising issues, self-defense, conduct by Siren and Hitoha, and his conclusion about the rule of law.”[2]
Hachiware: “So are we criticizing him?”
Judge: “No. We are taking the questions further. If you say ‘fraud,’ you must prove deception and intent. If you say ‘attempted murder,’ you must ask whether the fighters were defending someone. If you say ‘homicide,’ you must still examine necessity.”
Chiikawa: “Mmm… hard…”
Hachiware: “We’ll ask as we go!”
4. Does an unpaid 100× reward automatically mean fraud?
Hachiware: “If they promised 100× and did not pay, isn’t that fraud?”
Defense: “Suppose someone honestly plans to repay money tomorrow but unexpectedly cannot. Were they a fraudster from the beginning?”
Hachiware: “No… so we need to know whether the promise was a lie from the start.”
Prosecutor: “Exactly. Article 246 covers deception used to obtain property or an unlawful financial benefit. If the islanders never intended to pay, but used ‘100×’ to obtain dangerous labor for free, fraud becomes much more plausible.”[3]
Judge: “But 100 times what? Was it success-based? Was the hunt completed? Who promised payment? Was money set aside? Those facts matter.”
Prosecutor: “The advertising rules also depend on the relationship. Employment recruitment may trigger the Employment Security Act. Freelance contracting may trigger the Freelance Act’s rules against false or misleading recruitment information.”[5][6]
Hachiware: “So the flyer can be very suspicious without one automatic label.”
Judge: “Correct.”
5. Siren says the boat accident was not intentional. Is that the end?
Siren: “I was only playing.”
Hachiware: “If it wasn’t on purpose, no crime?”
Judge: “Imagine riding a bicycle at high speed without looking ahead and hitting someone.”
Hachiware: “You didn’t mean it, but you should have looked.”
Judge: “That is the basic idea of negligence. Article 209 addresses negligent injury.”[3]
Prosecutor: “A huge being moving through the sea may have had a duty to watch for boats.”
Defense: “Could Siren see the boat? How large was the area? How much stopping distance existed?”
Prosecutor: “The film does not establish all of that.”
Judge: “Then an accident is not automatically proof of criminal negligence.”
6. Hitoha: did she need mermaid flesh, or did she need the mermaid to die?
Prosecutor: “Hitoha, why did you kill the mermaid?”
Hitoha: “To save Futaba!”
Prosecutor: “That explains why you needed the flesh. Why did the mermaid need to die?”
Chiikawa: “Wah…”
Hachiware: “Oh…”
Prosecutor: “Did you ask, ‘My friend is dying. Could you give me just one piece?’”
Hitoha: “No.”
Prosecutor: “Did you know how much flesh was necessary?”
Hitoha: “No.”
Defense: “Futaba was dying. Hitoha was not a doctor or lawyer calmly comparing options in a courtroom.”
Judge: “That is why Article 37 and necessity matter. The question is whether there was a present danger, whether a less harmful realistic option existed, and whether the response was excessive.”[3]
Hachiware: “So ‘I was saving my friend’ matters, but it doesn’t end the analysis.”
Judge: “Exactly.”
7. “Just ask for one piece” is powerful — but it is still a question, not evidence
Hachiware: “It still feels like one piece might have solved everything.”
Defense: “Would the mermaid survive losing one piece?”
Hachiware: “I don’t know.”
Defense: “Would one piece save Futaba?”
Hachiware: “I don’t know.”
Defense: “Did Futaba have thirty minutes or thirty seconds?”
Hachiware: “We don’t know that either.”
Prosecutor: “That is why we would investigate dosage, nonfatal removal, time, communication, and other medical options.”
Judge: “A court cannot turn ‘maybe one piece was enough’ into ‘one piece definitely was enough’ without evidence.”
Rakko: “If you are going to punish someone, you do not fill gaps with guesses.”
8. What if the mermaid consented? What if it truly was one life against one life?
Hachiware: “What if the mermaid said, ‘Okay, I’ll give you a little’?”
Judge: “That changes a great deal. But consent does not make everything lawful. Article 202 separately addresses killing at a person’s request or with consent.”[3]
Hachiware: “And a small, nonfatal donation?”
Defense: “That is a very different legal problem from killing someone for tissue.”
Hachiware: “What if there truly was no alternative — mermaid lives, Futaba dies; mermaid dies, Futaba lives?”
Judge: “Then we reach the hardest form of necessity. Criminal-law theory may separate ‘Was the act legally justified?’ from ‘Even if not, can we fairly punish someone acting under extreme pressure?’”[3]
Hachiware: “So ‘Was it right?’ and ‘Should this person go to prison?’ can be different questions.”
Chiikawa: “…Wah.”
9. Siren is a victim — but can Siren eat possibly innocent islanders?
Prosecutor: “Siren, did you know every islander you took was the mermaid’s killer?”
Siren: “No.”
Prosecutor: “But you took and ate them anyway because the culprit did not appear?”
Siren: “Yes.”
Hachiware: “Losing a friend is awful, but…”
Judge: “That ‘but’ matters. A victim can become an offender in relation to new victims.”
Hachiware: “What about taking them away?”
Judge: “Japanese law distinguishes forceful taking from taking through deception. Article 225 addresses abduction or kidnapping for purposes including harming life or body.”[3]
Defense: “The loss of the mermaid still matters to motive and sentencing.”
Prosecutor: “It does not turn later revenge into self-defense.”
10. Can the islanders, Chiikawa, and Shima Jiro fight back?
Momonga: “If Siren eats people, we can smash Siren!”
Judge: “Not as a blanket rule.”
Hachiware: “What if Siren is attacking me right now?”
Judge: “If Shima Jiro uses necessary force to protect you, Article 36’s defense of another person becomes relevant.”[3]
Shima Jiro: “If someone is being attacked in front of me, I stop it.”
Chiikawa: “Wah…!”
Hachiware: “What if we expected Siren to come and prepared weapons?”
Judge: “Foreseeing an attack does not automatically destroy self-defense. A 2017 Supreme Court decision says the entire situation matters: prior relationship, expected attack, ability to avoid it, reason for being there, weapons, actual attack, and the defender’s purpose.”[7]
Rakko: “Preparing to survive is not the same as waiting for an excuse to kill.”
11. Chiikawa takes the stand — and crying still tells the court something
Prosecutor: “Did you know the mermaid-killing secret before arriving?”
Chiikawa: “…No…”
Prosecutor: “Were you actually attacked?”
Chiikawa: “Waaaa…!”
Hachiware: “They remembered and started crying!”
Judge: “Context makes the answer clear.”
Prosecutor: “Chiikawa’s group did not arrive as fully informed assassins. They were recruited and then caught in the danger.”[1][4]
Defense: “So each fight must be judged separately. Who acted, when, for what protective purpose, and with how much force?”
Hachiware: “What about Chiikawa realizing the truth and staying silent?”
Judge: “Article 103 focuses on active acts such as harboring an offender or helping escape. Mere silence after realizing something is not automatically concealment of an offender.”[3]
Rakko: “Not criminally punishable does not mean morally painless.”
Chiikawa: “……”
12. Futaba, the corpse, chimeras, and the Momonga identity bomb
Prosecutor: “Futaba, did you ask Hitoha to kill the mermaid beforehand?”
Futaba: “No. I was nearly dying.”
Judge: “Then benefiting from the act does not automatically make you an accomplice. Later silence alone is also not automatically harboring. Article 105’s special rule concerns relatives; friendship cannot simply be inserted into the statute.”[3][4]
Hachiware: “What about cutting up the mermaid after death?”
Judge: “Under our artificial assumption that the mermaid is a person, Article 190 on damaging a corpse may also become relevant.”[3]
Hachiware: “And chimeras?”
Judge: “If a chimera cannot understand rules at all, criminal blame may be the wrong tool. Society may still need capture or containment. Punishment and danger control are different systems.”
Momonga: “And me?”
Defense: “If body and consciousness belong to different beings, does responsibility follow the body, memory, or choosing mind?”
Momonga: “The cute one!”
Judge: “That test is rejected.”
13. “Rule of law” is persuasive — but then Rakko asks, Where are the police?
Prosecutor: “Kotake’s video ends with the importance of the rule of law.”[2]
Hachiware: “Meaning?”
Judge: “The victim should not become investigator, judge, and executioner all at once. Rules and neutral procedures are supposed to stand between injury and punishment.”
Hachiware: “Siren investigates and punishes. The islanders organize their own hunt. So accident → killing → revenge → more violence.”
Rakko: “Then where are the police?”
Silence.
Shima Jiro: “Where was emergency medicine when Futaba was dying?”
Silence.
Hachiware: “Oh. If you tell people not to take revenge themselves, something has to protect them instead.”
Judge: “Exactly. Medicine, investigation, courts, safe restraint of dangerous actors, victim support. The rule of law is not completed by putting a law book on the island.”
Chiikawa: “…Wah.”
14. Closing arguments and the one question left at the end
Prosecutor: “Suffering is not a license to harm. Hitoha may have confused ‘I need flesh’ with ‘I need a death.’ Siren moved from victim to creator of new victims. The islanders may have hidden danger while recruiting outsiders.”
Defense: “But do not use calm hindsight to demand perfect emergency decisions. ‘Maybe one piece was enough’ cannot become ‘one piece definitely was enough’ without evidence.”
Judge: “The court would first determine dosage, nonfatal removal, remaining time, medical options, imminence of Siren’s attacks, and whether the islanders truly intended to pay 100×.”
Judge: “On that basis: Siren faces a strong case for forceful abduction and homicide if the facts are proved. Hitoha’s act has the outward form of homicide, but necessity turns on realistic alternatives. Futaba is difficult to call an accomplice without prior participation. The 100× recruitment needs further fraud and recruitment-law analysis. Chiikawa’s group and Shima Jiro have substantial self-defense or defense-of-others arguments for reactive fighting.”
Hachiware: “So what is the one question connecting everything?”
Judge: “Was there really no less harmful way?”
Judge: “Could Hitoha ask for one piece instead of killing?”
Judge: “Could Siren search without killing unrelated islanders?”
Judge: “Could the islanders ask for help without hiding danger?”
Judge: “Could institutions intervene before victims started punishing one another?”
Chiikawa: “…Wah.”
A small cry.
Usagi: “Yaha.”
Momonga: “And the 100× reward?”
Prosecutor: “We still need a word with the islanders about that.”
Shima Jiro: “Anyone hungry can come to my place.”
Momonga: “You should’ve said that first!”
Judge: “Court adjourned.”
The film becomes legally interesting not because we can count offenses, but because it keeps turning victims into new offenders and protection into revenge. The deeper rule-of-law question is whether a society has medicine, investigation, courts, safe restraint, and victim support before people are forced into private punishment.
Sources
- 『映画ちいかわ 人魚の島のひみつ』公式サイト chiikawa.toho-movie.jp
- ORICON NEWS, こたけ正義感による映画『ちいかわ』リーガルチェック報道（2026-09-04） oricon.co.jp
- e-Gov法令検索・刑法（2026-09-01時点） laws.e-gov.go.jp
- Real Sound Book, 『映画ちいかわ』ヒトハ・フタバ・セイレーン周辺の整理 realsound.jp
- 厚生労働省・募集広告等に関する職業安定法の案内 mhlw.go.jp
- 公正取引委員会・フリーランス法特設サイト jftc.go.jp
- 最決平成29年4月26日・正当防衛の急迫性に関する判例資料（国立国会図書館サーチ） ndlsearch.ndl.go.jp
