*Before translation* I get the feeling either Marisa is finally going to tell Nitori how she feels, while Rinnosuke is asleep, so that she can get closure on giving up on trying to chase her, or possibly it'll make a "obvious reveal" moment, where Nitori casually admits she loves Marisa.
-Before Translation and not reading into it too much- really I think Marisa is going to try to pour her feelings out about Rinnosuke who she thinks is sleeping. Well after a time. Turns out the guy was in fact faking it and Marisa gets caught pretty much with her pants down...so to speak.
Who's with me on that plot? Show of hands? Please?
You know, there isn't any evidence that Nitori's relationship with Rinnouske is anything other than a business relationship. Even for how much Marisa worries over it, Nitori simply may not be interested in "stealing" Rinnouske from her in the first place.