Yōsuke is only ever heard over the phone, as he's away in India for work, which is what prompts Kōichi's being sent to Yomiyama in the first place. Though he's often cheerful and flippant with his son, on some level, Kōichi despises him, complaining to his aunt (and later Mei) about his lackluster parenting, which, among other things, has led to Kōichi becoming a proficient chef. Reiko doesn't seem to like him very much, immediately assuming he wouldn't support Kōichi's plans to attend an art college after high school. Kōichi's grandmother later told him Reiko had offered to take him in if Yōsuke didn't shape up as a father.
Yōsuke, being in India, isn't as strongly affected by the curse as those still in Japan, as he occasionally slips up and remembers Kōichi having been to Yomiyama before.