The person who called Ryuto to the gym at night was actually Maria. She confesses her desperation to become Ryuto's first, even if that means dressing and acting like Runa. Ryuto is shocked. As the two talk it out, someone else watches from the shadows.
I get why Maria fell for you. I really do.
verstehe ich Marias Gefühle am allerbesten,
als sie sich in dich verliebt hat.
Je suis la plus à même de comprendre
les sentiments de Maria à ton égard.
capisco perché Maria
 si sia innamorata di te. Davvero.