Hiroshima is already guaranteed to finish in the top two positions for the year and be promoted to J1, and also cannot be passed by Yamagata, currently in second place.
The current standings:
1st Hiroshima 81 points with 7 games to play
2nd Yamagata 59 points with 7 games to play
3rd Sendai 58 points with 8 games to play
Even if 2nd place Yamagata wins all remaining games and Hiroshima loses, Yamagata will be one point shy of the championship. However, 3rd place Sendai has the game in hand. If Sendai wins all remaining matches and Hiroshima loses all remaining games, or if Hiroshima draws one and loses the rest by a terrible scoreline, Sendai would be champions of J2 this year.
Hiroshima plays at Osaka on Sunday, and at the same time Sendai hosts Mito. While Hiroshima's championship is an almost certainty, more than a few channel surfers will flip back and forth between the matches to see what happens. Hiroshima fans likely have no strong feelings toward Mito in preventing a Sendai win this Sunday (and maybe some fans would actually like to see a Mito and Hiroshima loss, so Hiroshima can clinch the title in the home stadium?), but I know many Yamagata, Shonan, Tosu, and Osaka fans are going to pull for Mito to win this match.
Will there be a J2 champion crowned on Sunday at about 3PM? It may end up resting on if Mito can defeat Sendai for the first time ever... in any capacity.