i think the author has read ahead
I think they may have different ways of speaking in japanese? ie. Rei is blunter
ohhhhh
possible
his way of speaking and his expression is softer. Plus they while rei says he felt mutsumi integrate, kazuha has been saying (to koutarou earlier) that they dissappear.
how did the translators know that he's kazuha and not rei on the last scene ???? sorry im just curious(⊙…⊙ ) also if he's kazuha does this mean rei is the real host????