The real issue here, imo, is that it is Nana's job as the domme to make him feel comfortable and make her feelings clear. Yes, he is passive, but it's not really up to him to pursue her. He has given up his vulnerability for her while she has remained on top, guarded and safe. She has not assertively refused this other guy, just vaguely told him to leave, nor has she made it any step towards building a connection with Sawada. Like I've said elsewhere, the typical male-female dynamic where the man pretty much exclusively is responsible for pursuing and making the woman comfortable does not work in a femdom context.