I was investigating the setting of DLC during my vacation.
It was able to be successfully downloaded by debugging, and it could also be registered in the Steam MUSIC library.
A soundtrack folder is created in the "Moe Mekuri SP - Moe Turtle SP -" folder.
There is MP3 and text of lyrics inside that folder.

I will release it if approved by Steam.

The difference from the soundtrack CD is as follows.
・Moe Mekuri 1 - 3 Sold as each soundtrack.
　(Moe Mekuri 3's soundtrack CD also includes Moe Mekuri 1)
・Only vocal songs are included.
・Offered with MP3 sound source.

Price is slightly higher than CD.

Moe Mekuri 1 VOCAL COLLECTION　 2.99 USD
　Track List:（Short version）
　01 Pure
　02 Love Potion
　03 Love Prison
　04 Honey Trap
　05 Under World
　06 Halation World

Moe Mekuri 2 VOCAL COLLECTION　10.99 USD
　Track List:（Long version）
　01 Adieu
　02 Clone Amy
　03 Crazy Diver
　04 Endless Silence
　05 Pure
　06 Love Potion
　07 Honey Trap
　08 Love Prison
　09 Under World
　10 Halation World
　11 Melty Color
　12 Love Eater

Moe Mekuri 3 VOCAL COLLECTION　7.99 USD
　Track List:（Long version）
　01 Honey Beats Boy
　02 Summer Gas Burner
　03 Escape
　04 Crispy Love
　05 Try Try
　06 Love Potion
　07 Honey Trap

Soundtrack CD is for Japan only.