High School DxD
High School DxD is the best ecchi battle harem out there, turning teenage fantasies into a real power system. Issei Hyoudou is an openly perverted high school student who is killed on his first date by a fallen angel. Rias Gremory, a beautiful crimson-haired devil princess, then brings him back to life as a devil. He has the "Boosted Gear," a legendary dragon artifact that makes his power grow by leaps and bounds. He says his goal in life is to become a "Harem King," and the show takes this very seriously. The series really sticks to its premise: Issei's perverted motivation literally powers his fighting skills, making his horniness a tactical advantage. There is a lot of unnecessary fan service, but there is also surprisingly good world-building, like the three-faction war between angels, devils, and fallen angels, as well as dragon politics and mythological conflicts. You can have real high-stakes drama and complicated supernatural lore even when your main character's power-ups are triggered by breasts. Not the least bit ashamed and very aware of it.
