Top 3 in Top 10 smartest characters in anime Dr.Stone.
Byakuya Ishigami is one of the few survivors after the petrified weapon turned all of humanity to stone. After becoming an astronaut, Byakuya lived in outer space, which kept him from being affected by the petrification process.
He is Senku's biological father's best friend, but he is the one who adopted him. Although they are not related by blood, Byakuya really loves Senku. Byakuya has been dead for thousands of years, but his relics still help humanity, especially Senku. Byakuya is not as intelligent as Senku, but he still has a vision of the future of humanity. So, before he died, he collected all the things needed for Senku even though it took decades.