Groups
- onsoku 4
- oobari doujou 4
- oomorian 4
- open road 4
- opera 4
- opereperkep 4
- orange girl 4
- orange honey 4
- orange mill 4
- ore no genkai 4
- oreaji 4
- oreism 4
- organic mill 4
- oriental lattice 4
- oroca 4
- orukaniumu haigou a-jou 4
- osacanasanteam 4
- osakana milk tea 4
- oshikko channel 4
- oshimai 4
- osushi 4
- otaut-r 4
- otimpons 4
- otokonoko fantasy club 4
- otoriya 4
- oumi rengou 4
- over 4
- over network unit-k 4
- overcrowd 4
- overrun 4
- owan 4
- oz 4
- oz project 4
- ozawa kobo 4
- p 4
- p and p 4
- p.y.l... 4
- paiwohasa-mu 4
- palm tree soft 4
- pan no mimi 4
- panda scanners 4
- pandion 4
- pantsu hakanai 4
- pantsu koubou 4
- papapapapaon 4
- paper tiger 4
- parabola 4
- paranoia-fact 4
- parapara no chahan 4
- party balut 4