|Release|Artist|Title|Notes|Album|
|---|---|---|---|---|
|2004|Hiroshi Itsuki feat. Rimi Natsukawa|Deigo to Hanasu (デイゴとはまなす Talking with a Tiger's Claw Flower?)||Onna no Ehon|
|2005|Chikuzen Sato with Rimi Natsukawa|Boku no Mune de Oyasumi (僕の胸でおやすみ Goodbye with My Heart?)|Features on "Rimits: Best Duet Songs" (2006)|The Selection of Cornerstones 1995-2004|
|2005|Rimi Natsukawa|'Aa Kōshien' Kimi yo Hachigatsu ni Atsuku Nare (「あゝ甲子園」君よ八月に熱くなれ You Make Me Hot in August (from Ah, Kōshien)?)||Ningen Manyōka: Yū Aku Kashishū|
|2005|Kaoru Kurosawa duet with Rimi Natsukawa|Manten no Hoshi no Yoru (満天の星の夜 Night with a Sky Full of Stars?)|Features on "Rimits: Best Duet Songs" (2006)|Love Anthem|
|2006|Andrea Bocelli duet with Rimi Natsukawa|Somos Novios (Ai no Yume) (ソモス・ノビオス～愛の夢 It's Impossible (Dream of Love)?)|Features on "Umui Kaji" (2007)|Amore (Japanese Edition)|
|2008|Taiyo Yamazawa presents Rimi Natsukawa|Utabito (歌人 Singer?)||Music Tree|
|2009|Chage with Rimi Natsukawa|Boku wa Dō Kana (僕はどうかな What Should I Do?)||Many Happy Returns|
|2009|Rimi Natsukawa|Tada Sore Dake (ただそれだけ It's Only That?)||Katsuhisa Hattori|

Question: which year had the most titles released?
Answer: 2005