Well, shamelessly suggesting mine as it has most of what you requested, though there's a slight twist.
It's a reincarnation type novel, but the twist being she was reincarnated to the past (just several years back).
It's a slice of life though I skipped the baby years, glossed through the first 11 years of life and it kinda picked up in their teen till adulthood.
It's completed, 907 chapters, has some action, a little bit of humour, slow romance, it does touch on LGBT issues, and the FL isn't revealed until Vol 3 or 4 or something. I can't remember. /heh
Title: New Life: Second Chance