Yamiochi Yuusha no Haishin Haishin: Tsuihou sare, Kakushi Boss Heya ni Hourikomareta Kekka, Boss to Tansakushagari Haishin wo Hajimeru @comic

It's been fifty years since dungeons first appeared on Earth. In the present day, dungeon exploration and live streaming have become commonplace. Kuga became a dungeon explorer alongside his close friends, but because he's a "jack-of-all-trades, master-of-none" hero, he ends up getting banished from the party. In his despair, Kuga is tossed into the hidden boss room, which is rumored to be impossible to return from alive. There, he encounters Alicia, a vampire beauty. He prepares himself for death, but Alicia seems very interested in human streaming, and asks: "Could you teach me how to stream?" With nowhere to go, Kuga reluctantly agrees to Alicia's proposal, and they start an unprecedented explorer-hunting stream. For some reason, their stream goes viral at an abnormal rate, and an unknown power awakens in Kuga...? Meanwhile, something strange is happening to the party members who banished Kuga... (Source: Shogakukan, translated)