It was "Marumaru na Kanojo ni Dekiaisarete Imasu", or
"I am doted on by my 〇〇 girlfriend"
It went all pretty well and was very cute, but then out of nowhere a fiancee of the FMC appeared, and that arc dragged on too long.
Then it was ended really quickly, with the MMC basically rejecting his feelings for the FMC. Probably because the serialization was ended prematurely.
It was a massively disappointing ending to a pretty promising RomCom