Ever since Unohana's return from a recent mission, you felt like she's hiding something. And she was, most probably

So being bored one day, you decided to check and maybe find out what it is, where you saw your fellow Captain Saito, holding into the doorframe, like literally holding as she helf herself on it, leaning to try and look behind Unohana who was standing in middle of her room as she hid Zaraki from her. Its probably for the best