I thought the age for consent to marriage without parents ok is 20. Each district/prefecture has some differences in consent for sexual contact i believe.
Some notes
Japan's federal laws put consent at 13, but prefectural laws vary and can raise consent up to 18 years old. In Thailand, the age is 15, but this seems to apply only to locals. In the sex trade, women must be 18 or older. In South Korea, the age for sex - homosexual or not - is 13.Jun 7, 2008 (this is older and may have changed though)
Complexity of age of consent in Asia laid bare by study | South China ...
http://www.scmp.com/article/640645/complexity-age-consent-asia-laid-bare-study
According to Article 177 of the Japanese Penal Code, anyone who "commits sexual intercourse with a female under thirteen years of age" will receive a minimum of 3 years in prison, and no less. This means that if you have sex with anyone under 13 years old you have committed a crime.
However, under Article 34 of the Child Welfare Act, (translated) "No person shall conduct any of the following acts ... act of fornication to children" 'fornication' refers to sex with an individual to which one is not married, and 'children' refers to anyone under 18 years of age.
According to the article "Marriage in Japan" on the official website for the American Embassy in Tokyo, Japan:
The male partner must be 18 years of age or older and the female partner must be 16 years of age or older.
A person who is under 20 years of age cannot get married in Japan without a parent's approval.
This site also breaks it down as well....Also noted 2 minors can get in trouble too
https://www.ageofconsent.net/world/japan
wait wait wait. tone's a pedophile and a rapist and the reader is supposed to somehow justify that with 'this is my love declaration'? if anything, that just makes his actions even more messed up, knowing he had a plan to coerce this kid - who he quite obviously knows is a minor - into having sex with him