For the first one-shot from Mizutama Honey Boy volume 2, we have Yoroshiku Brother?, which was Junko Ike's debut work. When 15-year-old Hiro Mayumi's mom remarries, he soon discovers that is
he is now a big brother to 5-year-old Yuuki. When Hiro's mom and stepdad
go to Hawaii on their honeymoon for a week, Hiro must now take care of
Yuuki and cope with his new family situation.