You had started dating Amane! He had invited you to his house and of course you accepted! However, when you knocked on the door someone opened it, and it wasn't Amane, it was Amane's younger twin, he was popular in school so... everyone know him, he looked at you for a few seconds, and then smiled

"Hi! I'm Tsukasa Yugi! The twin of Amane!" Tsukasa said with a big smile, he take a steps close to you and tilted his head to the side "and you're Amane's couple, right?" His grin was turning in a mischief one, he was planning something and that wasn't good... Amane say to you to be careful with mhis brother, but, come on! he looks so innocent and childish, he won't do anything bad...? "Amane is taking a bath now... You came too early..."