Source: Kyō Channel
Like other internet challenges the Tawawa Challenge (たわわチャレンジ tawawa charenji) requires that you upload a video of yourself performing the challenge to YouTube or a social media platform. As for the challenge itself, it's extremely simple. In fact, it's so simple it can be summarized in the following two steps.
Get your hands on a smartphone.
Place the phone on top of your breasts. If it stays you passed the challenge.
This peculiar internet challenge began in October of last year not long after manga artist Kiseki Himura (Twitter) tweeted an illustration of an anime girl with a smartphone laid on top of her breasts. This illustration was part of a series of drawings called getsuyōbi no tawawa (Monday's Tawawa) and this is where this challenge got its name.
As for the word tawawa, it is typically defined as "(of a branch heavily laden with fruit, etc.) drooping; bending" (WWWJDIC). However, as you've probably figured out by now, it is also often used to describe large breasts.
Although Himura didn't come up with the challenge himself, it seems that his October tweet was enough inspiration to give birth to #たわわチャレンジ (tawawa charenji) and.along with the birth of this hashtag came plenty of videos featuring Japanese girls placing smartphones on top of their breasts.
Not surprisingly, many of the people participating in the Tawawa Challenge are Japanese gravure idols (swimsuit/lingerie models). One such example is, Erina Kamiya. She is both a member of the Japanese idol group Kamen Joshi and a model. In the video below, which was uploaded to the official Kamen Joshi YouTube channel, Kamiya shows us what a successful Tawawa Chellenge video looks like.
The vast majority of Tawawa Challenge videos are like this. However, there are a few interesting exceptions. For example, Anna Tachibana, also a Kamen Joshi member (and Trump Kamen member), uploaded her own Tawawa Challenge video to the Kamen Joshi YouTube channel. However, her video is quite different from Kamiya's.
Obviously, it's a bit difficult for most men to participate in this challenge, but the popular Japanese YouTuber Kyoichiro (official channel) did, and the results were, simply put, hilarious. If you'd like to skip straight to the Tawawa Challenge portion of the video just skip to about 1:20. The first minute or so is Kyoichiro talking about a previous internet trend, PPAP. He then transitions from that topic to the topic of the Tawawa Challenge. Make sure to watch all the way to the end.
Interestingly, modelpress, in an article published on January 4th noted that this internet trend may be seeing a resurgence in popularity. Whether this is actually turns out to be the case though, remains to be seen.