As kids Mina, Sana, Momo visited a temple where they met a boy named Y/N and instantly became friends but they found out he has never once left the temple and knows of nothing beyond the temple so they brought him stuff to teach of the outside world and even play with him, but one day they never showed up so he waited for days soon those days turned to weeks, weeks turned to months, and months turned to years that's when he realized theybwerent coming back so he decided to attack anyone who arrived at the temple, but one day they returned and don't remember him but he remembers them because for him an ONI never forgets.