In Witch's Briar Castle at the end of Chapter 5, Towa, Rion, and Gorou are the only characters to not be under the life draining effects of the labyrinth like the rest of the students and faculty. This may seem odd at first glance, but once you progress further in the story and learn about their circumstances, you then realize that they all have justifiable reasons for this. Towa is also a shrine maiden at the Kokonoe Shrine, and thus, has enough spiritual awareness to perceive the Eclipse, and be granted automatic immunity from the ill effects of the labyrinth. Rion is a host of an Angel-type Grim Greed that is more powerful than the Mist Witch, so she's probably protected from the labyrinth's effects by the Seraph of Despair. And finally, Gorou is already a Wielder by default, since he's also the commander of Zero Battalion Aegis; the JSDF's special task force] Suddenly, it all makes sense as to why they're not affected by the labyrinth.
On a side-related note, Jun was among the people comatose during the Witch's Briar Castle dungeon. As it turns out, Jun is really White Shroud, a very potent Wielder agent for the church. It seems weird that he'd be faking being sick and have enough time later to meet with Mikuriya, but a throwaway line when he's admitted to the school infirmary reveals that the body in the dungeon at the time was a double made by magic.
Jun's friendship events seem like pretty mundane events on a first playthrough, with the occasional odd moment here and there. It's only when you find out he's White Shroud and learn his situation do you realize what was actually going on. When he moved to Morimiya he was detached and basically emotionless due to his position as a Seal Knight, but his time with Kou & company made him experience and grow to the point that his initially fake persona became real. Those mundane bonding events were about him trying to figure himself out as a person without cluing Kou in to what was going on.
A running message in this game is that the loner mentality is neither healthy or mature. The gameplay on two side story chapters really drives this home. The first one is White Shroud's solo mission after chapter 1, where the dungeon has a surprisingly steep difficulty spike that can make players struggle even though Shroud is a clearly powerful character - really driving how much harder it is to do this job when you're by yourself. The second one is Asuka's solo side story. There's no difficulty spike and she has a powered form- but it comes at the cost of her HP constantly depleting so you could die if you aren't careful.
