Mahou Shoujo Nante Mou Ii Desukara.  

Mahou Shoujo Nante Mouiidesukara, I've Had Enough of Being a Magical Girl, 魔法少女なんてもういいですから。, Mahoii

Yuzuka Hanami is an ordinary girl who enjoys life despite her parents' demanding jobs. Her mother rarely stays home, but Yuzuka remains cheerful and focuses on being a top student. Meanwhile, Miton is an alien with the power to turn his master into a magical warrior. However, there aren't as many enemies now, so he's been out of work for some time. Struggling with hunger and homelessness, Miton has made his home in a garbage pile. One day, while Yuzuka passes by, Miton offers his services to the young girl. Although hesitant at first, Yuzuka agrees, but she's taken aback when she transforms into a magical warrior wearing a swimsuit.