Frankly speaking, both reading the manga and watching the anime, the only moment I liked Kei was in the last few minutes of episode 11, where she tells Aika the real thing.
What I would like to happen:
- Kei takes care of Airi and leaves Wataru and Aika to sort themselves out on a date or something and they will end togheter.
What I would like to happen to end the anime in an OK way:
- Wataru gives his gift of a shell necklace (?) to Aika.
- Airi and Kei don't get in the way of the MC couple, and if they stay together (I highly doubt it will happen...) I'll think it was a success, if there was a kiss between the two of them then it will even exceed my expectations (not that they are many for tell the truth).
What I think will actually happen in the last episode:
- Wataru goes to Aika's house.
- Airi will be able to bring the two together.
- Kei will interrupt them at an important moment.
- The anime will end with an incredibly open ending, because someone didn't have the balls to make a closed ending for an anime that probably won't have a second season.
Also:
Sasaki still the best girl!