My Classmates Are All Time-Travelers

One day, Yang Yu suddenly discovered that many of his classmates had traveled to different worlds, some to the late Ming Dynasty, some to the Tang Dynasty, some to the Great Qin Dynasty, and even novel worlds such as Siheyuan, martial arts, and Xianxia. Yang Yu can contact them through WeChat, chat, send videos, and even give items to each other by sending red envelopes. As a result, Yang Yu became rich.