The other couple is 18 (Daichi) and 15 (Princess Eldora). Closer, but younger. Both couples are outside the "half + 7" rule, for those who care about such things.
I didn't realize the 'levels' were ages, heh.
considering how long it took before feelings became stated
I feel the in-manga time has been at most a few months, if that?
a terrible age gap. I alr dropped the villainess
Which one? "Please Bully Me" is very vague about Yvonne's age-at-death. But WataOshi is like 25+ and 15, and maybe ditto Fed-Up Office Lady (though in this case the younger age is obscure.)