Mitsu is Kanaria's medium and basically lives and breathes dolls. Her entire room is basically a doll shrine—shelves packed with them, constant trips to the doll shop for gifts—and she dotes on Kanaria constantly. At work she's technically an office lady, but Kanaria introduces her to the other dolls as a professional photographer, which fans find amusing given how little that actually describes what she does.
Her real passion is doll fashion. In the manga, it's revealed she ditched her stable office job to become a pattern maker for doll dresses, selling her work through her website "Angels Cage." It's way more work for way less money, but it's what she wanted to do. She and Kanaria are cut from the same cloth—equally harmless and weird.
Mitsu only shows up in Träumend and the manga, not the rest of the anime. She also has freckles in the manga but not in the anime adaptation.
As for Jun, they never actually meet in the anime. But in the manga, Kanaria drags her to the Sakurada house where Mitsu immediately starts calling him "Junjun." She notices he's genuinely talented at dress design and making, and tries to partner with him. He turns her down.
Content compiled by AnimeList.moe from publicly available sources.
