I am seriously wondering who actually is the target that will pay attention to the product placement in their webtoon ?
Like why would a fictional character know about how great a skincare product ?
I get it it is to put your brand name in the mind of the reader but how many people even bother to read the name of the product ?
I can't answer you that, but how many people do read brand names on any ads no matter where they are really? People who are curious will look stuff up people who aren't won't that how ads work these days ^^" But fact is that with all of the ad blockers and video on demand stuff people are more likely to read webcomics and your brandname there than ever ^_^
Using fictional characters for ads is quite common in both Japan and China and not a new thing - be it through webtoons/webcomics or even actual television or theater commercials and even promotional posters on the streets and billboards - one of the most famous things to exist are the Louis Vitton commercial using Lightning from FFXIII as a model, there's also a lot of restaurants or even car brands that have collabs with anime production studios or gaming studios (take for example Genshin Impact) and run commercials and ad both on TV and Youtube.
There are also for example a lot One Piece commercial (mini episodes) featuring famous brands like Nissin, KFC, Fanta, Nissan, Cine mike pop corn, XFit.
People were/will be standing in line to get the goodies and order especially the food related stuff.
(Mosspaca Advertising Department is a manga here in which the artist's Moss, Old Xian, Tan Jiu (坛九) talk about there experience making these small ad comics. )