The whole thing starts because Koganei says that they should all visit Kiyoshi together at the hospital, as a team, for New Year's. Mitobe thinks of the quiet sadness that permeated the hospital the last time they visited, of how extra quiet the sadness will feel on New Year's, and agrees readily.
Mitobe is embarrassed to find that – making their way through the brightly festooned corridors of the hospital on the 2nd of January – the place actually feels less sad on New Year's. Even sick people wants to celebrate, he berates himself.
Koganei, because he is Koganei, smiles cheerfully and says, "Don't mind, Mitobe! I'm sure Kiyoshi will be very appreciative of us coming!"
Mitobe nods back. Kiyoshi is Kiyoshi and he will be very happy that they came to visit. He won't be anything but happy to see them – even if he's actually feeling sad; but that's something they can work on, there are still more than two years left of high school.
"I'm sure Kiyoshi will trust us soon," Koganei says sympathetically. He shoves a hand into the suspiciously bulging bag he had brought along. "Anyway, I was thinking these might help!"
Mitobe looks down at the handful of good luck amulets and New Year's arrows in Koganei's fist. Belatedly, he remembers that Koganei had taken a lot longer than the rest of them when they'd visited the shrine as a team to pray for the New Year and Kiyoshi's health earlier that morning.
He lets the uncertain twist of his mouth do the talking for him as Koganei explains how the talismans and arrows would make great decorations for Kiyoshi's hospital room, it'd really brighten up the place!
Up ahead, the door to Kiyoshi's room is open and Hyuuga is already shouting at him about something or other. Which is lucky for Koganei, because Hyuuga would have a lot of words about using holy ornaments as decorations. Hyuuga is pretty traditional, Mitobe has found; maybe it's because of his obsession with history.
Izuki finally gets Hyuuga to stop blocking the doorway, allowing Mitobe and Koganei their first look at Kiyoshi since the New Year. He looks fine. Still like he is forcing himself, but not as desperate about it. Tsuchida is standing on one side of the bed, showing him the box of bunny-shaped apple slices that Mitobe knows had been made by Tsuchida and his girlfriend together.
"Sorry it's not osechi," Tsuchida says apologetically as Kiyoshi laughs him off.
On the other side is Riko, staring enviously at the perfectly shaped slices, while besides her Izuki tries to make a pun about apples only to be interrupted by Hyuuga's dope slap.
Mitobe takes up position by Tsuchida, exchanging a smile with him, then with Kiyoshi, as the three of them watch Koganei convince the others into putting up the shrine charms as decoration after all. Hyuuga is uncooperative to the end, but bows under the pressure of both Riko – who jumps at the chance to be able to do something helpful – and Izuki – who is already making puns about them.
Tsuchida laughs softly, nods at first Kiyoshi, then Mitobe, and goes to join the fun.
Kiyoshi only allows himself to cry a little once everyone's attention is solidly fixed on putting up the decorations. But he lets Mitobe hand him a tissue and that is enough.
Osechi are a set of special dishes for New Years; they're not exactly at a level where you'd expect teenagers to be able to make them.