Shun is sharing his tangerine and ends up going to Kaname's house, but Chizuru, Yuki and Yuta end up going too and all 5 stay for dinner. While it was expected they would leave after dinner, instead at Chizuru's suggestion, it becomes their first 5 person sleepover.
Besides, you guys don't 
have a change of clothes.
Porque no tienen ropa para cambiarse.
Porque no tenéis ropa para cambiaros.
Além disso, vocês nem 
têm mudas de roupa.