Purchased Files from OTOTOY https://ototoy.jp contains Link to OTOTOY's album page.

M4A & FLAC:

Brought to you by OTOTOY.JP http://ototoy.jp/_/default/p/524467:lyricist=やなぎなぎ

Brought to you by OTOTOY.JP http://ototoy.jp/_/default/p/1086381

MP3: (timestamps are modified)

::Sun, 01 Aug 21 12:34:56 +0900 from http://ototoy.jp/_default/p/70198

::Fri, 01 Apr 22 12:34:56 +0900 from https://ototoy.jp/_/default/p/70198

I think it would be good to find by regex like https?://ototoy\.jp/_/?default/p/([0-9]+), and normalize it (like https://ototoy.jp/_/default/p/$1) then search MusicBrainz from URL.

some notes:

• previously OTOTOY adding wrong URL to MP3 files, like http://ototoy.jp/_default/p/70198 (missing / on _ and default). Fixed at 2022-03-15 https://twitter.com/ototoy_info/status/1503683773829107713
• previously OTOTOY adding HTTP URL instead of HTTPS URL even after website supports HTTPS. Fixed at some point (maybe same time as fixing MP3 comment?)