[ZeroForever]

are you referring to Ren/Run from To love ru?
edit : nevermind you gave a artist name I don't recognize YUI Toshiki
wiki has the listing for his works, so i would assume their one of the below but i don't have the time to search through them all.

Mermaid Junction (マーメイド・ジャンクション?) (1987)[n 1]
Tadaima Hāto Konsenchū (ただいまハート混線中?, Confusion of the Heart) (1988)
Umauma (ウマウマ?) (1990)
Misutei Gaaru (ミスティガール?, Misty Girl) (1991)[n 2]
Jankushon (ジャンクション?, Junction) (1993)[n 3] (Incorporated into Hot Tails, Vol. 1)
Kirara (1993–1997)[n 4]
Hotto Jankushon (ホットジャンクション?, Hot Junction) (1993–1994)
Yui Myūjiamu: Yuo Toshiki Shoki Sakuhin Shū (唯ミュージアム　唯登詩樹初期作品集?, Yui Museum: The Early Works Collection of Toshiki Yui) (1995)
Ikenai yo Yūkosan (いけないよゆう子さん?, Don't Do It, Yūko-san) (1996)
Uindingu Pātī (ウィンディングパーティー?, Wingding Party) (1990)[n 5] (Incorporated into Hot Tails, Vol. 2)
Itto (イット?, It) (1999)
Yui Shop (1999–2003) Kodansha[12]
Re Yui (2000)
Toraburu Jemini (とらぶるジェミニ?, Trouble Gemini) (2000)
X2 (2000)
Princess Quest Saga (2000)
Kagome Kagome (かごめかごめ?) (2000–2001)[13][14]
Suna no Kami, Sora no Hito (砂の神 空の人?, God of the Sands, People of the Sky) (2002)
Boku no Futatsu no Tsubasa (ボクのふたつの翼?, My Two Wings) (2003–2005)
Honjitsu no Osusume Pura du Jūru (本日のオススメ　プラ・ドゥ・ジュール?, Today's Special: Plat du Jour) (2004)
Mai no Heya (MAI の部屋?, Mai's Room) (2006–2008) Kodansha[15][16]