You know, using the "lucky pervert route" as development for someone that only looks at 2D is usually something I don't mind, but when it's used at their ages(13/14), it's a bit...I don't know...iffy. I think I can count on my hands how many times it HASN'T gone this route.
I do hope the mangaka shows MORE development in other ways that don't involve one of the girls going "Woops, here's my body/underwear!".