Kei Yasuda has written several songs, but none of them have been released on CD.
This is a list of songs that have been performed live or on radio:

nacchi wa nee (@Young Town Doyoubi, 2001 and 2002)
Dear My Friend  (@Young Town Doyoubi in 2001 and 2002)
Happy (Performed sometime between 2009-2012 by Yaguchi and Yasuda, at live OG events. A live video of Yasuda singing the song is availabe on the DVD M-Line Memory)
もう一度I miss you (@ Kei Yasuda & Mari Yaguchi Special Live 2010 -Kimi ni Todoke 13nenme e no Kansha!!-)
きみへのうた~Always Love (@Yasuda Kei Birthday Live 2012)

Nacchi wa Nee. 

なっちはねぇ。 (Romaji: Nacchi wa Nee. English: You See, Nacchi She.) is a song written by Kei Yasuda. It is an R&B breeze pop. song lyrics heartwarming story. mismatch feelings.

It was never released on cd, but was only performed on air on MBS Radio on April 7th, 2001. A large fan base held petitions trying to achieve a cd release for it, but that never happened.

Credits; Lyrics: Kei Yasuda, Music: Kenji Tamai

Dear My Friend

Dear My Friend is a song written by Kei Yasuda. It is a medium ballad.

It was never released on cd, but was only performed on air on MBS Radio on March 30th, 2002. A large fan base held petitions trying to achieve a cd release for it, but that never happened.

Lyrics: Kei Yasuda, Music: Kenji Tamai

Happy

Happy is a song written by Kei Yasuda and Mari Yaguchi. It was first presented as an original song at the live show Yasuda Kei & Yaguchi Mari Special Live 2010 -Kimi ni TOdoke 13nenme e no Kansha!-. A live video of Yasuda singing the song is availabe on one of the DVD M-Line Memory releases).

Lyrics: Mari Yaguchi | Music: Kei Yasuda | Arrangement: TAKAROT

Mou Ichido -I miss you-

もう一度I miss you (Romaji: Mou Ichido I miss you; English: One More Time -I Miss You-) is a song written by Kei Yasuda. It was first presented as an original song at the live show Kei Yasuda & Mari Yaguchi Special Live 2010 -Kimi ni Todoke 13nenme e no Kansha!!- 
 

Lyrics & Music: Kei Yasuda | Arrangements: TAKAROT
Blog post with lyrics

 Kimi e no Uta -Always Love-

きみへのうた~Always Love (Romaji: Kimi e no Uta -Always Love; English: A Song to You -Always Love-) is a song written by Kei Yasuda. It was first presented as an original song at the live show 保田圭Birthday Live 2012 held on December 23rd, 2012.

Lyrics & Music: Kei Yasuda