This is a very silly Dorem. Does anyone know if this comic is part of a larger collection of “Detective Doremy” stories?

Unsure, but here's the original work in Pixiv;

[漫画]迷探偵ドレミー[C90おまけコピ本] | へき(癖) [pixiv] https://www.pixiv.net/member_illust.php?mode=medium&illust_id=58580442

All of the suspects are the only ones that ever visit Sunzaan on a daily basis lmao