Your happy ending - BNHA x Mreader ff

M/n was the twin brother of Kai but people could always tell them apart by M/n always having a smile and Kai straight faced.
M/n always felt bad for eri in fact he was the only thing that ever made her smile.
But when other come she is full of sadness . M/n always tried to find eri a way out but Kai and his buddy's always caught them. Kai never hurt his brother because his brother was there with him his whole life. But what happens when hero's come to save eri.