Biochemical weapons aren't covered by the Geneva Conventions. They are covered by the Geneva Protocol, a completely separate treaty. Japan has been party to the Geneva Protocol since 1970, as well as the Biological Weapons Convention (1982) and Chemical Weapons Convention (1997). (It has also been party to all 4 Geneva Conventions since 1953 and amendment protocols I and II since 2004. The only part of the Geneva Conventions it's not party to is AP III, which just adds the Red Crystal to the Red Cross and Crescent as an ICRC protective sign.)
TakoyakiMajor damageThat was really...NothingHieeee!Ri-kyunAkagi?AdmiralNot herePoiExplosion I-classDogI-classSo fast!hot!Cut it out already since it's embarrassing! CurryNo.Everyone!I don't think so!?*wag* *wag*Ri-classHoppo and her Fan-ClubAdmiralCurry!?ShockMy third turret is...a Takoyaki!?Secret weapon...Go...Major damageHoppo-chan is so cute!CurryHiei curry!Uwaaah!I-I dodge it!Hoppo-chan and the CurriesI thought...Criminal I-classI threw that away already.Don't call me takoyaki!I-Is that...*steaming hot*Takoyaki CurryTastes like takoyaki, poi.Shimura, behind you!nano death