@TheOrigArcade said it best. Taking what he said for granted:
The priorities are important. Do you want Mitsu to have the regret that his family emergency brought his club down from winning, or do you want the friend group to not be broken up? Is the mission more important, or the friends who made the mission to push themselves?
There is no perfect answer. Either way, something gets sacrificed.
Did I mention I love this manga more? Life's hard. Growing up means owning it and adapting to it. You have to be clearheaded like Chika and Sensei, but not too imposing to alienate others. Friendships are only so strong. These trials can forge them tighter.