If the couple is composed of two consenting adults who just happen to have been born in different generations, that can be acceptable, but when a show features a relationship between an adult and a child, warning sirens should be going off.
This is especially true of anime couples with big age gaps, as their relationships rarely feel consensual. Even though they're works of fiction, many anime relationships are alarmingly unhealthy. Sadly, it's not uncommon to find anime lovers who are 10 - or even 20 - years apart from one another.
