Youta wanted a friend, so obviously, he summoned one. He didn't quite count with the fact that he'd summon Mumu, a mighty and evil dragon girl, notwithstanding that due to hundreds of years of imprisonment, she's very needy, very weepy, very clingy, and lonelier than the button "9" on a microwave oven.
Youta and Mumu become friends. They both have no other friends and are emotionally desperate, though Mumu's desperation is focused on moreso than Youta's. Mumu acts like a little girl blustering and bragging and wanting to get praised. Fe latches onto and enjoys any show of affection from Youta. Fe waps feir tail and wiggles it around in giddy excitement. Fe tears up and cries a lot. Fe is needy and dependent and doesn't have any of the sort of dignity or maturity that you would expect from a three hundred year old dragon. And I guess that gap is supposed to be cute? But it honestly just puts fem squarely in the "loli" box, without even a semblance of mental aging. The series essentially just consists of the two of them validating their friendship and expressing their enjoyment with each other. The chapters are only about four pages long apiece, so it's very short. At first, the nice artwork and cutesy dynamic made it a pleasant and enjoyable read (let's call it a 6/10), but it didn't take very long for that initial luster to wear off and leave me more bored by the relationship than anything. It's not a horrible read or anything, but I don't think it's a very solid one either. [Reviewed at chapter 13]