Under17 (アンダーセブンティーン、アンセブ) was a popular Japanese duo, which included Haruko Momoi and Masaya Koike, that wrote and performed many moe songs that are featured in anime and video games. The lead singer, Haruko Momoi, is well known for her unique vocals and catchy lyrics. Some of the anime series where Under17 songs have been featured are DearS, Kujibiki Unbalance, Tenbatsu! Angel Rabbie, Mouse, and Popotan. This group has released several adult videogames' opening songs. On September 27, 2004, it was announced that Under17 would break up, with Momoi and Koike going separate ways due to creative differences.
- Koi no Milkyway (Milkyway2) (Game)
- Ichigo Go!Go! (Ichigo Da) (Game)
- Nostalgia (Majokko a'la Mode) (Game)
- She・Know・Be ～Koi no Himitsu～ (Nin Chikku Haato) (Game)
- Tsurupito na Koi (Suku Mizu ～Fechi ni Naru Mon!～) (Game) + *Tsu
- Mouse CHU Mouse (Mouse) (Anime)
- Popotan-Batake de Tsukamaete (Popotan) (Anime)
- Gem Stone (with Funta) (Popotan) (Anime)
- Love Slave (DearS) (Anime)
- Kujibiki Unbalance (Kujibiki Unbalance) (Anime)
- Utamaru Ekaki Uta!
- Kagayaki Cyalume
- Natsu da! Umi da! Suku Mizu da!
- Koi no Recipe
- Watakuchi wa Celebrity
- Icchae! Popotan
- Saisho to Saigo no Magic
- Purin no Uta
- Remon no Tokimeki
- Koko da yo.
- Angelic magic
- Kimochi Tomaranainai
- Watashi wa Miko-san Cupid
- Okashi na Onnanoko
- Which do you choose?
- Figure ni Naritai
- Uwaki Shite mo Eeyo ~Fickle Mix~
- Tsurupeta-san Irasshai ~OYOYO Version~
- Mii-tan no Mahou de Pon!!
- Otome no Mahou de Pon-De-Ke-Wa
- Motto, Yume, Miyou!!
- Rabu Kero Panikku!
- POPOTAN KISS
- Ganbare! Tama-chan
- Kyouryuu Shoujo
- I.n.ter.riMOUSE ~Optical Mix~
- Samishi Kunai Mon
- Hajimete no Natsu
- OS NO YES
- Under17 Best Album 1 Bishōjo Game Song ni Ai wo!! - Lantis LACA-5235
- Under17 Best Album 2 Moe Song wo Kiwameruzo!! - Lantis LACA-5236
- Under17 Best Album 3 Soshite Densetsu he... - Lantis LACA-9045
- Under17 meets Witch Vol.1 - Witch WIC-7427
- Under17 meets Witch Vol.2 - Witch WIC-7428
- Mouse chu Mouse - Mouse no Theme - Lantis LACM-4083
- Love Slave - Lantis LACM-4135
- Popotan e.p. - Lantis LACM-4099
- Kyouryuu Shoujo
- Popotan Maxi Single
- Popotan Character Song - It's A POPO Time - Lantis LACA-5216
- Dream Party Songs
- Pajamas Soft Collection
- "FanimeCon 2009 Announces Halko Momoi (Musician, Songwriter, & Seiyū) as a Guest of Honor". News. Anime News Network. 2009-05-14. Retrieved 2009-05-22.
- "RJP-Pro Anouncements [sic]". News. Anime News Network. 2004-06-08. Retrieved 2009-05-22.