From MangaHelpers:
Arusera is an angel who has fallen from the heavens during a nap outside. She crash lands into Kousuke’s bedroom, who has imagined this kind of scenario out from a video game or movie in his head with a naked girl. Arusera is extremely comfortable in her own skin and loves being naked. She is extremely curious as to what love is and how it feels like. She wants Kousuke to show her what it means to love. But people aren’t going to let a gorgeous angel, literally, just walk by, especially when that girl is already nude.