According to Lens:
Splash art text: "After bathing / A night with beautiful women."
And yeah. Tsukasa really doesn't get Nasa at all. He literally had no interest in any of this stuff before she came along. He's said so many times. I suppose she just struggles to accept a young guy like him would be so devoid of any sex drive outside of one person like he is. He's literally Tsukasa-sexual, not heterosexual. Kinda like Grace from EGS being called 'Teddsexual'.