Series: Suzumiya Haruhi no Yuuutsu - Bunny Mikurun Breeding Diary (Tokiomi Tsubasa)

Original title: ウサギみくるん飼育日記
Artist: Tokiomi Tsubasa
Source: Pixiv search

Koizumi got a mini-Mikuru bunny for a pet, a pet that is almost too moe for him.