There's also Bounonji, where they start dating and evolving half-way through the mange
That one where the teacher clones a female student and one of the clones start dating the MC.
Gantz did have relationships and evolved.
Sakuranbo kiss not only does that but adds a threesome loli to the spin.
Fucking Beastars has proper character and relationship development.
There are several examples, it's jsut way less than the ones doing SoL or simple romantic comedies.