OOC Is Serious Business / Bleach

• Brilliant, but Lazy Shunsui Kyoraku is a Martial Pacifist who never loses his temper, and his general demeanor never really elevates beyond "mildly concerned"—even when fighting his mentor who is implied to be thousands of years older than he is. However, when his Heterosexual Life-Partner Ukitake appeared to have been killed, he lost it, dropping everything to try and kill the Arrancar who impaled him. For extra emphasis, even in the context of that story arc, his reaction was pretty extreme. Later on, when Yamamoto, his surrogate father figure, is killed in battle, he wails his name at the top of his lungs to the sky.
• Chizuru Honshou is the local Genki Girl and Plucky Comic Relief. She has only cried twice in canon, both times when attacked in unusual ways: the first was when she was subjected to Body Horror by Numb Chandelier that made her attack Tatsuki and Orihime; the second was when Aizen was chasing her and her classmates — her ability to see the spirits is only revealed because, like Tatsuki, Keigo, and Mizuiro, she remains awake during Aizen's attack on Karakura Town, but unlike them she has never been told what's going on and is therefore terrified.
• When Ichigo decides to murder Tsukishima (despite never having killed anything other than hollows^note which sends their spirits to the afterlife, so he's doing them a favor at this point) on the off chance it will reverse his Fullbring's effect on his friends and family, you know he's pissed.
• The usually cool-headed Byakuya completely loses his composure when As Nodt exposes his fear of losing Rukia.
  • Not long after, when Ichigo finally arrives at a devastated Soul Society, one of the first things he does is check on Byakuya to make sure he's not dead. After Ichigo reassures him that Rukia and Renji are still alive, Byakuya uses the last of his strength to beg Ichigo to save Soul Society, while apologizing for his "audacious request".
• Much earlier on, on June 16, Ichigo begins acting oddly friendly to his classmates, and Orihime immediately picks up on the change, impressing her best friend and Ichigo's long-time friend Tatsuki, who took three years to figure it out. It's because it's the day before the anniversary of Ichigo's mother's death, which he blames himself for.
• When the Vandenreich have invaded Society, Yumichika publicly uses kido and very nearly reveals his true shikai, despite knowing that the battle-obsessed Eleventh Division wouldn't approve.
• Zangetsu (specifically, the side that reflects Ichigo's Quincy-ness) is normally pretty stoic and aloof. But when Ichigo's despair literally floods his inner world and weakens him in battle, the sword spirit makes his anger at his wielder's weakness loud and clear.
• If Gin Ichimaru stops smiling, it's notable. If he stops smiling and opens his eyes? Shit just got real.
• The first opening theme of Season 2 shows Rukia in prison, utterly downcast because she's about to be executed by her own people. Up until that point, she had been confident and fierce in all situations, including while fighting to the death against Hollows and while forced to try something no Shinigami had ever done before — train a human. So seeing Rukia despairing is an effective signal that the plot is not fucking around anymore.
• Ichigo notices this when his younger sister Karin tearfully begs him to help Yuichi, a young boy who watched his mother die, and whose spirit is trapped inside a bird. Ichigo recalls that after their mother died, Karin's twin sister Yuzu stepped up to do the housework, but the only thing Karin could do was toughen up and not cry anymore. Ichigo hadn't seen Karin cry in years, so he instantly understand how upset she is.
• Kenpachi Zaraki is not exactly known for expressing anything beyond annoyance at fighting weaklings or excitement at the prospect of fighting a Worthy Opponent. As such, the extent to which he respects and admires Unohana, the First Kenpachi only really becomes clear when he sheds a Single Tear at the thought of dying without defeating her, and later screams at her not to die after he succeeds.
• Mayuri Kurotsuchi is known to disregard the well-being of allies and has a major Berserk Button around having his science equipment messed with. When the Zero Squad announces they’ve broken into his lab and his only reaction is calm acceptance, you know you’re dealing with a squad of badasses.