MY SECOND SENIOR BROTHER IS A MORTAL BUT STRONG is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Cheng said, "They ascend during the day, and I find it hard to sleep at night." Junior Sister curiously asked, "Why can't you sleep if others ascend?" Eldest Brother quickly replied, "Because he has helped others to ascend while he himself is still a mortal." A second later, the Eldest brother, who was in the Tribulation Transcendence realm, passed on to the other world.