冨樫先生 refers to 冨樫義博(TOGASHI Yoshihiro), the author of Yu Yu Hakusho, Level E, and Hunter X Hunter. On May 24, a recently registered twitter account posted with a picture of some drawing work in progress that

とりあえずあと4話。

meaning

As for now only 4 episodes left.

The user’s nickname is 冨樫義博, thus everyone familiar with manga understood at once that the post is referring to Hunter X Hunter, one of Shonen Jump’s most celebrated manga of all time. It has been over 1200 days (more than 3 years) since the last new episode of Hunter X Hunter, and fans all over the world have more or less given up on the hope of seeing the new story of Gon (well as of now more likely Kurapika). This twitter post just dropped the bomb.

Of course netizens question the genuineness of this suspicious account, since there is no solid proof on the picture that it came from Mr Togashi himself. But later other famous manga artists like MURADA Yusuke retweeted and verified that it was Mr Togashi , and voice actors like ISE Mariya (the voice for Killua Zoldyck) posted a picture of Killua crying. The community then realized that this is really happening, and heated up through tweeting, causing the tag 冨樫先生 to trend.

Learn more about Hunter X Hunter on wikipedia. Also, check out this youtuber 樽江突撃 who’s been practicing 1000 punches EACH DAY during the absence of new contents of Hunter X hunter for over 2 years. His efforts have paid off TAT.