Shinrei Tantei Yakumo - Volume 2 Chapter 1

Upon being reborn, she immediately offends a vicious two-faced bigwig.

A man is reborn into the world of Avatar: The Last Air Bender as a waterbender from Katara's tribe. Best of all, he was the same age as her, and he had a system with him to help.He knows the future and a system that lets him continuously get stronger by completing quests or long-term missions, as well as giving him the ability to copy abilities from others for himself. He will become invincible in the world of Avatar, even more so than the Avatar himself.

Cheng Yin likes her deskmate Chen Yan for a long time, but she never dared to confess her love for him, and the phrase ‘I like you’ is a secret hidden in her heart, but she can’t help but blurt it out from time to time…
Cheng Yin: “Chen Yan, I’ll whisper something to you.”
Chen Yan always leans over quite cooperatively, “What?”
The words came to her lips, Cheng Yin blushed and changed it into: “Your pants are unzipped.”
Chen Yan: “?”
Later, this kind of useless whispering has become more frequent, and Chen Yan listened again without moving a bit: ” Speak.”
The day of the party, Cheng Yin drink for the first time, Chen Yan became two in front of her eyes, she grabbed the person with both hands, want to try to catch the real Chen Yan, only to have her hand caught, he lowered his head in her ear and said: ” Let me whisper to you.”
Cheng Yin: “…… what?”
Such bad behavior, she thought it was something bad, Cheng Yin checked her pants and made sure the zipper was closed before she lean over.
The man’s breath blew softly in her ear, laced with a bit of the smell of wine.
“I like you.”

- Description from Novelupdates

The NPC sets out on a journey to defeat the Demon Lord, joined by beautiful girls he meets along the way.---This is an NSFW story, so if you're under 18, turn back now, son. No NTR, and no full-on Yuri. There might be slight Yuri—like girls kissing and stuff during threesomes—but it's not that kind of Yuri where the girls fall in love with each other while in a relationship with the MC.---