I'm just a fan of web novels and can't provide all the music of the anime Death God. However, I can tell you some of the famous music in the anime Reaper, such as "Soul Slayer" and "Elegy of Souls". If you want to know more about the music of the anime Reaper, you can consult the relevant literature or consult professionals.
The music of Su Muqiu's death was " Drop ". This song was Brother San's Doujin song, sung from Ye Xiu's perspective. It was adapted from Jin Guisheng's " Between the Rainbow " and covered by Little Soul. This song described the scene of Su Muqiu and Ye Xiu dying in a car accident on the day they turned 18, as well as the short and warm time between them. The lyrics expressed Ye Xiu's longing for Su Muqiu and his memories of Glory.
While waiting for the anime, you can also click on the link below to read the classic original work of " Full-time Expert "!
One idea could be a rengoku fanfic where he trains a new group of young slayers. It could focus on his unique teaching methods and how he instills his values in them.
Tanjiro would be a great character to pair with rengoku. Their different personalities could create an interesting interaction. Tanjiro's kind - hearted nature and rengoku's fiery determination could lead to some great storylines.