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Takamura and Yuu-kun make me think: Murasakibara (Kuroko no Basket) and Nagisa (Free!).
OMG TRUE
I agree on Nagisa, but Murasakibar for all his childish behavior and sweet tooth is still more mature (and sweet mother of yaoi I never thought I would say such a thing).
More specifically for chapters 2 4 and 11. All really pretty art styles.
My reply is kind of late but if it is still actual or if it helps someone else...
You can find the list of the each chapter and its author here : http://www.mangago.me/read-manga/kemono_jingai_bl/mf/v01/c001/3/ ! (⌒▽⌒)