As title states. Willing to read isekai/transmigrate... all those other's that are overly done at this point but would also prefer not to if at all possible/can be helped

Honestly the romance doesn't have to be the main focus of the plot but there should be some, at least more than say

Edward and Winry

TYIA

Gin no Saji
Horimiya
Basically anything by ADACHI Mitsuru

Shigatsu wa Kimi no Uso
Baby Steps
Koe no Katachi
Molester Man

Some of my favorites that fit what you're looking for:

Amano Megumi wa Suki Darake!
Boku no Kokoro no Yabai Yatsu (still ongoing, but I don't foresee any harem elements)
Change 123
Dorobou-chan
Negative Happy Chain Saw Edge

All are completed series, with the exception of Boku no Kokoro no Yabai Yatsu.

Second Boku no Kokoro no Yabai Yatsu.

Taisho Wotome Otogibanashi
Karin
Change 2!!

Maybe Zeroin, Carnivorous Princess Yegrinna

I forgot all the good shounen ones, but I should still remember some seinen ones.