You have to date someone for them to be an ex. So no. No concerns there. The only ex Katsuya has ever had was from an alternate dimensional Raccoon City and he hasn't seen her in years now.

"The language barrier makes things complicated." He nods as he splits a pair of chopsticks and digs in to his food. Normally he dislikes eating out (too critical of how they make their food when he can cook at home) but sushi is a rare treat and one he quite enjoys. "Is this the past for you?" Katsuya tilts his head to the side slightly. "I hadn't stopped to consider that time would also be different." But of course it would. Alternate dimensions.