Drunken Goddess Reflux Theme Song: DEMON’S SHOT

The quick answer

DEMON’S SHOT is the theme song. Aiobahn +81 composed and arranged it. DEMONDICE wrote the lyrics and sang the vocals.

Song credits

DEMON’S SHOT is the theme song. Aiobahn +81 composed and arranged it. DEMONDICE wrote the lyrics and performed the vocals.

English captions: In the music video, open Settings → Subtitles/CC → English.
Timed transcript: Expand the YouTube description and choose Show transcript.
Lyrics on one page: Open the DEMON’S SHOT lyrics on Uta-Net.