So many Vietnamese books and you are lazy to find a good one? Check this out: "Dế mèn phiêu lưu ký".
It's a fucking good story about the adventure of a character named "dế mèn". He did not isekai and has no harem. In the first chapter, he is a bAd GuY, harass female ones and killed his neighbour. After that, mèn had been kidnapped and force to beat the shit out of another character. However, his xiến tóc the barber gave him a weird hairstyle.
He is a sMart guy, after some attemps, he exits that place successfully. He became a nice guy and travels. He met his m8. The m8 named dế trũi. They travel togethet but don't have sex, what a disappointment. They protecc but also attacc. Then, they trapped themself in the middle of a HuGe mega extra thicc river. They decided not to starve together.
They saved themself but shit them out because a wild enemy appeared.
……
That's a nice story to read. I love Tô Hoài -sama.
<This is a beatiful love story.