So what is the plan author-san? Are you gonna pull an epic plot twist and show that "akshually, none of the girls really liked him after all xd" or where is this going?
my guess is, mc ends up with the middle.
with the timeline being.
Mc thinks middle is the girl from the past.
youngest sister confessed and got rejected.
and the oldest came clean about her being the girl of the past. and suggested that she should honor her promise. but also got rejected. then came clear it was a test afterwards. and roots for him and the middle.
mc and middle gets together.
the youngest openly flirt with him.
the oldest keeps having happy accidents with him
and the middle needs to protect her boyfriend form her sisters, while crashing breast first in to him.
pretty sure i read multiple endings like this one before.