Papaoutai
It's a french song but it's pretty popular people so you guys probably know it it's about a son talking about his absent father.
It reminds me how Shion's father is absent his whole damn life like get back to your son now you mean old man
anyway I was half kidding I'll find better songs when I'll have free time! <( ̄︶ ̄)>
(I should really get back to my duties )