I think it was on purpose for the next installment. It was short and at the end it makes you think, what does kijima actually feels deep inside? We never got to know but this short movie makes you curious on purpose on what his facial expression meant. Even when they are happy finally being together something is bother Kijima, Is he still yearning for kido while being with kuzumi or was it because he's still hurt with no confidence on taking this happiness he wants that kuzumi puts out for him or he's scared of hurting kuzumi. lots of possibilities only with that one facial expression, damn they are so good.