While there is some discussion on who was involved in BGM production, I added SONO MAKERS based on the tweet by Umigame
"というわけでSMEEさん最新作 OPとBGM一部をSONO MAKERS様にて担当させていただいております！！ 前回に引き続き作品に関わらせていただき光栄です！！ 今回も自信作なOPとBGM、ぜひぜひよろしくお願いします！！"
https://twitter.com/redumigame/statu...91768714002432
Although this only states part of the BGM is by SONO MAKERS, the staff roll does not credit anyone else.
https://www.youtube.com/watch?v=RqYiTZ-YS-k