Upon finding out that Aizen managed to consume the real Karakura Town, the 10th Division was mobilized into King's Realm, where Hitsugaya encountered Hinamori. Despite her physical recovery, she was still mentally unstable after Aizen tried to kill her; she rejected the truth, refusing to believe that Aizen had betrayed Soul Society of his own volition and instead blaming Ichimaru. She tried to convince Hitsugaya to speak with her former captain and save him from Ichimaru's control. Naturally, Hitsugaya refused, but nothing he said could dissuade Hinamori from desiring to approach Aizen to bring him back to his senses. Then, she decided that she'd directly approach Aizen herself. Hitsugaya engaged in a short battle with her to protect her from both Aizen's forces and herself. After knocking her out, he left her in the care of other subordinates before heading out to the big battle.
It's hard to recall or detail exactly what happened, but the Gotei 13... had lost.
And so, Hitsugaya returned to life as captain of the 10th Division... which was surprisingly normal, save for retrieving survivors and burying the dead. And frequent meetings while the remnants of the Gotei 13 tried to gather their bearings, select a new commander general. And maybe overall cleanup of destruction when Aizen managed to take the real Karakura Town.
Oh yeah, and his grandma died. It'd been a painful loss.
Occasionally, he'd wind up seeing Hinamori. Outwardly, he brushed off the fact that they'd yet again engaged in another battle while locking all the hurt and pain inside.
Life had been affected, but was otherwise relatively normal. But that didn't mean that Hitsugaya had accepted it. Like others, he didn't have any intention of remaining under Aizen's thumb. But different folks meant different strokes; though there were many who opposed Aizen, there was no full agreement to methods and motives. Some favored one way over another.
Regardless, he could not -and would not- forgive Aizen's betrayal...