
At first I thought I’d hate Vivi, but she’s grown on me, I was worried it was gonna go the harem route but she seems more like a little sister/daughter

Okay so the thing is I have NOT read the novel BUUUT according to the tags they have on novelupdates.com there is NO harem tag, so hopefully that can answer your question. (⊙…⊙ )(〜 ̄△ ̄)〜
I might consider reading it after I finish the-world-is-overflowing-with-monster-i'm-taking-a-liking-to-this-life novel, but feel free to check this manga's novel out in your own free time!(๑•ㅂ•)و✧(⌒▽⌒)
Novel ?
https://page.kakao.com/home?seriesId=50594147&page=1
Here is the only novel link I could find but I think for most of the chapters I think you have to pay but since its in Korean you may need a translator device or something as it won't auto google translate.
(Tested it myself on a free chapter.)