Umi's struggling to maintain just enough self control to avoid sneaking a leering peak in the baths or kissing her in a room full of other people. Pretty sure a trip with just the two of them would would be very different.
And why did no one question her on how she knows what love at first sight feels like? I was hoping she'd nervously glance around, happen to look at Shou and at least one of them would realise.