Rin and Len was making a potion in the Sekai cuz they were bored but they didnt realize they were making a love potion. Later, Len and Rin heard KAITO calling them so they left the potion on the table and they ran to KAITO.

Meanwhile Rui was Running for a reason idk, then he saw a drink, I mean he was so thirsty that he didnt know it was a love potion. As he sipped on it he started to feel weird and when he looked a Tsukasa he started to feel attracted to him

“Tsukasa-kun~”