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 after their national tour, with Momoi and Koike going separate ways due to creative differences. Their final concert was held on November 20, 2004 at the Yokohama Blitz.
- Haruko Momoi (vocals, lyricist, composition)
- Masaya Koike (guitar, arrangement, composition)
- Tenbatsu! Angel Rabbie (Tenbatsu! Angel Rabbie) (Anime) and (Game)
- Angelic magic (Tenbatsu! Angel Rabbie) (Anime) and (Game)
- Koi no Milkyway (Milkyway2) (Game)
- Ichigo Go!Go! (Ichigo Da) (Game)
- Icchae! Popotan (Popotan) (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)
- Mouse CHU Mouse (Mouse) (Anime)
- Popotan-Batake de Tsukamaete (Popotan) (Anime)
- Gem Stone (with Funta) (Popotan) (Anime)
- Hajimete no Natsu (Hourglass of Summer) (Anime) and (Game)
- Love Slave (DearS) (Anime)
- Kujibiki Unbalance (Kujibiki Unbalance) (Anime)
- Kagayaki Cyalume (Kujibiki Unbalance) (Anime)
- Utamaru Ekaki Uta!
- Natsu da! Umi da! Suku Mizu da!
- Koi no Recipe
- Watakuchi wa Celebrity
- Kyuryuu Shoujo
- Saisho to Saigo no Magic
- Purin no Uta
- Remon no Tokimeki
- Koko da yo.
- 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
- 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
- Popotan Maxi Single
- Mouse chu Mouse - Mouse no Theme - Lantis LACM-4083
- Ganbare! Tama-chan/Magi-Cu
- Popotan e.p. - Lantis LACM-4099
- Pajamas Soft Collection
- Popotan Character Song - It's A POPO Time - Lantis LACA-5216
- Love Slave - Lantis LACM-4135
- Kujibiki Unbalance (OP & ED Single)
- Dream Party Songs
- "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.
- "MOSAIC.WAV & UNDER17 Tenbatsu! Angel Rabbie (Live)". 2009-07-29. Retrieved 2014-08-21.