kiriya is like 15 - 16 yrs older than hikki. So back then when they were married, hikki was around 19 (i think she married before 20..), and kiriya was around 35ish..
So if she's dating something only 9 yrs older than her, it's not that extreme to me..
. You know, kiriya didn't look too old when he stood beside hikki (he does have a look), and hikki tried to wear something to fit him. That is why I felt her fashion taste was actually kinda bad during that era... She always wore something too old for her.
The bottom line is. Kiriya and hikki may have a 16 yr gap, but in appearance they don't (sorta like... 7 - 8 yrs apart). It will be funny if she's really dating that 9 yr older man, and in appearance they look like 15 yrs apart
(some people do look old you know..)