The author loves to kill people to drive the plot. The grandpas, but also Atsumu's grandma died early. Akira's both parents died. Satowa's father died (and maybe her grandparents are also dead since they apparently weren't around to help the family in any way). Of course Chika's parents are as good as dead, but at least the author didn't actually kill them, to avoid things getting too ridiculous.The grandpas are dying T-T