There’s one thing Nakanishi-kun says in this conversation that bothers me a bit: “Yes, the contract should already be finalized as well.”(はい もう契約も済んでるはずです)
This wording is strange, because when we saw Sakura moving out, the time on Shinobu’s phone was 1 p.m., while the meeting started at 8 p.m. Seven hours had already passed in between—more than enough time for anything to have been completed. If, as he says, Sakura is now in his apartment, then they should already have met and exchanged information about what happened outside while Nakanishi-kun was absent. If the agreement had already been signed, he should have stated it with certainty, rather than saying “should already.” And even if Sakura had not confirmed it with Nakanishi-kun, Izumi Anka should have confirmed it with him via LINE, so it shouldn’t have sounded like a guess.