I Became Invincible After Sweeping The Floor For 70 Years - Chapter 879 - : Acknowledge Master

A man who was once called the world’s strongest agent ended up becoming a teacher after his retirement, to train a new generation of agents. After many years of training his disciples, he was killed at the age of 60 by a secret organization’s ruse and was reincarnated in another world with his memories intact. Though he was surprised by the existence of magic and the strange species in that world, he quickly adapted to his condition as a newborn and took advantage of it. He acquired special magic and gained a massive amount of strength thanks to his rigorous discipline, in order to reach his goal: Resume his career as a teacher which he left halfway through in his previous life. This is the story of a man, who, based on the memories and the experiences of his previous life, became a teacher who travels through the world with his students.

Gou Liang was originally a small office worker of the Space-Time Administration Bureau but because of a weird questionnaire, he was sent to multiple worlds in order to complete a mysterious and arduous mission — to use the correct posture to awaken lord god.

A chance to change, to challenge destiny, making dreams a reality, and live a legend! A regular man gains a system that allows him to turn into a fish!

- Description from Novelupdates

An incredibly athletic older brother, Tenryu Taiga. A programming genius girl, Tenryu Fuyuki. The two siblings separated for eight years ended up living under one roof again after facing the problem – a lack of funds for living expenses.

Fuyuki proposes a way to earn money, a core system deeply involved in people’s daily lives, a game that awards you money as a prize for defeating malicious bugs in cyber world, the 《Aries》structure. Taiga after becoming a warrior in the game relying on his inborn senses, is puzzled by the unfamiliar sensation.

One day Saionji Rui, Fuyuki’s best friend appears and is attacked by a mysterious bug― “I’ll be waiting, my prince.”. Hybrid fantasy battle of cheating siblings begins here!