I thought the same! If I remember correctly, in anime they showed a short scene at first, when swimming club was going on this training camp and everyone around was asking if Makoto is fine with training in an ocean. It wasn't said why he should dislike that, just minor tips. And then they showed the extended scene when Makoto is explaining to his clubmates what happened in the past. So I thought, maybe in the light novel author could do the same, and he'll explain to us later who was that girl etc. Of course not in such circumstances ;)

Btw, I'd like to know how Zaki-chan looks :)) Damn, I read this chapter today, preparing for translating it, and the whole time I was like, "Ah, it's so like Haru" or "Wow, Haru was so much more social in the past"... I really really like the Haru and Makoto then, this light novel really is needed :D :)