Nobody's making a two-episode ONA to promote an album, so when it happens, it's either a tax write-off or someone genuinely loved the bit. This one feels like the latter, chibi characters doing dungeon comedy while the actual musicians behind the OP/ED get to be themselves, just tiny. It's fanservice for people who actually care about who made the songs they've been replaying.

Ore dake Haireru Kakushi Dungeon gets a pair of short ONA collaboration episodes starring the musicians behind its opening and ending themes. The performers appear as small, chibi-style versions of themselves, and the shorts double as promotion for their albums. One episode features Spira Spica and the other features Coala Mode. Both are light comedy pieces with a fantasy flavor, built as promotional extras alongside the main series.