Ok...this is a bit messed up. Forget the age gap and all the problems that'd create, this would be serious trauma for the son/friend. The girl you've been friends with forever and are starting to think might be into you a bit is actually after your mother.
The romance between the highschool girl and the mother is developing actually rather nicely. With these kinds of premises you kind of have to bullshit the romance to be two-sided but this one actually does it well.
Damn i really like age gaps cuz im into that shit, yuri cuz im a cultured man, and weird situations like sisterxsister or childhood friend x mom like here cuz im a degenerate, so this is perfect.