For those who don't know, the reason this isn't being updated on mangadex, but is on other sites is because it has a paywalled official English translation. I haven't really looked into mangadex's policies, but I know that lots of translation groups refuse to continue translating when books get official translations. Mangadex, unlike other Manga sites out there, relies on the translation teams to upload (or not) chapters. Other sites don't give a damn about the authors or translators, so they just directly rip releases from official channels. If you find Tappytoon's monetization strategy distasteful as I do, you can easily read all currently released chapters with a quick Google search. If you want to support the author and translators you can click the official English link above. Either way you can still keep track of your reading progress manually here on mangadex.
This series starts slow, with awkward artwork and dialogue, but it gets really good starting from around ch.50. The artwork, story, and dialogue all really pick up and now I can't get enough. >_<