I don't know why you're talking about japanese people, webtoon is originally a naver product which is Korean, Line is a subsidiary of Naver, and Tapas is originally korean but based in the US so mostly stuff that is korean has had "Big breaks" with Netflix series and the like, but usually comics like Kingdom and True Beauty, with some american/british comics becoming international hits like Lore Olympus and the previously mentionned Heartstopper.
Like Darthmongoose said, Tapas isn't where novels are usually the most published, and they tend to be cross-published on more novel-oriented spaces, with most online massive hits coming from wattpad and fanfiction.net of all places (After, 50 Shades, The Kissing Booth...).
I know someone who was supposed to be published traditionnally through wattpad in the french space after winning a watty but it turned sour really fast because of how they treated her, she would be considered as "making it big" but it was a horrible experience for her. Again like Kate said it depends on what you consider "a big break", does it have to be a publishing deal? Or a film adaptation? Or a radio series? Does it only count if it goes international? Or is staying domestic ok? Do you have to enjoy it? Is it worth it if you don't? For me anyone who has enough following to self-publish their own series and make money off it is already up there with some pretty high opportunities, but is rarely framed as "making it big".