The Weakest Student is Actually the Strongest Sage 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.cc fastest updating comic site. The Summary is

People around me called me a sage who was obsessed with the Philosopher's Stone." There was once a man who mastered magic and was known as a sage. Realizing that creating the Philosopher's Stone was impossible with his current body, he took a gamble. He decided to reincarnate into a future world as a different person to obtain a new, stronger body. His reincarnation was successful, and he gained the body of a cute boy named Mars, marked with the emblem of strength, the "Pure Seal." However, in the future, this emblem was inexplicably regarded as a "Defective Seal"...! All for the sake of the Philosopher's Stone. The journey of the strongest sage begins anew!!