Shouldn't this be one word? (no space)
I think I always submitted in one word.

ref.
https://www.jleague.jp/
https://www.jleague.jp/en/

FYI, NO-INTRO and Wikipedia use "J.League".

Dunno, J. League looks more stylistically correct, imo.

CTRL+F "J.LEAGUE PUB Report" on this page this page, seems to be J.League without the space.