He was mentioned before the future arc when the ten year bazooka was used on I-Pin. She would always say how she had to deliver noodles to Uncle Kawahira before they got soggy.
After the Vongala escape the Choice Game, they are chased by Zakuro. Intending to look for a realtor named Grandma Kawahira for safety, they go to the realtor's house and meet Uncle Kawahira. He helps them escape from Zakuro by using his Hell Ring to create a fake murder intent which leads Zakuro away to Mt. Fuji.