From Easy Going Scans:The story of a boy and girl whose lives were one day entwined by red string. Literally. 2r181g
52 + 1 Chapters (Complete)

Very slight spoiler ahead, stuff that happen within the first 5 or so chapters.
There is a limit to how a mangaka or whatever can overlook common sense when trying to force the story forward and this one got annoying in just 4 chapters. So, the author needed bad guys, so they just happen to be stalking the house, and just happen to to be able to spy with binoculars through the window which the owners just happend to leave the curtains open when conducting thing they must be kept secret at all cost and just happen to care sht about exposing a critical weakness of our poor main char which might as well cause his death... oh! and you can kill someone by pulling a string from their chest..., cut the crp. And as if that wasn't enough they just happen to forget a reel of string that glows and costs 300.000.000 yen and is equivalent to who knows how much lifespan of the MC..., this is no longer just forced, its ridiculous and pathetic, and it doesn't stop there.
Equally pathetic is the complete omission or if preferred, acknowledgement by omission that the doll masters are above the law... so they can kill, kidnap, attack in open day, steal, etc, and nop, nothing happens, you are on you on MC pal, laws don't apply to doll masters!!
Last, the MC is annoying and doesn't make much sense, there is too much going about that should at least, at minimum, make him angry yet he just lowers his head and accepts it as nothing, even it he's in love with Yuran it doesn't make sense, he "may" forgive Yuran but the rest? And he can get angry, he does on several occasions, so, it doesn't make sense.
The author had a somewhat interesting idea (not great, mind you) but completely ruined it by his lack of storytelling, coherence and consistency.
Yup, quite good......not without flaws, but overall quite good. A good mix of characters, a story line that runs consistently throughout (and holds its secrets well until the end)........yup, in particular for one of the Korean webtoons, very much worth reading.
And hey, one that's essentially a shounen story that doesn't run 572+maybe 500 more chapters......yeah, those are few and far between and always worth checking out 😀
It's not entirely without merits, but this is mostly a standard shounen story with ecchi elements. Neither the protagonists nor the antagonists act all that smart; and in the finale, a not insignificant part of the story takes the antiquated stance that striving for immortality is intrinsically bad.
Oh, not to mention that the protagonist is ridiculously overpowered / talented (he's the only doll master who can control dolls without any long-term adverse effects on his health), and the author hardly even bothers with explaining that.
In other words: This story is utterly mediocre, cookie-cutter shounen.