Danbooru-based image board with a specialization in high-quality images.
bikini chikotam delivara! parasol stick_poster swimsuits yufu_sumika

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Not sure if this is chikotam or narumi yuu.
Narumi Yuu didn't work for this game.
Narumi is credited on a couple of the illustrations in the arbook though. Their styles are somewhat close to my eyes, so I couldn't call it. Was going to tag it chikotam, but I'm just not 100%
Not a couple, just one page like other "guest artists".