You know what would be a good plot twist? If the flashback girl is not who he chooses. I mean, it seems perfectly reasonable considering his past is just the past and the quintaplets now are the ones he care about.
@ss4chris yeah, we never learn. The mangaka is the one that made nisekoi spinoff. 2nd Nisekoi didn't have to mean it's "story" is similar to Nisekoi. Maybe it's from artstyle perspective, maybe fanbase overlap, or whatever.
@ices im pretty sure thats what ppl meant by nisekoi though. promise girl but girl chosen isnt the promised girl dude to bonding with non promised girl.