Somehow, Chika being the more passive one between these two doesn't sit right with me. Especially not when Riko is usually so... meek? Not the same kind of meek Ruby is but in a sweet bookish/art loving girl + future waifu/mother material kind of way. Even Maru, who's an actual librarian, can't compare with Riko when it comes to having that bookish girl aura.
Oh well. I love ChikaRiko either way.