Relatively mild, especially compared to the majority of harem shows.
When Yamada first switches bodies with Urara, he runs into the girl's restroom and strips down to her bra and underwear. It is implied that he then looks at her bare breasts (the camera cuts away, but we hear his excited reaction and see a comic nosebleed).
When girls switch bodies with boys, there are some jokes about "strange things" in between their legs.
A few mild bathhouse scenes (only the outlines of breasts are seen).