Thoughts on this concept

[Level 5s existed at the pinnacle of all espers in Academy City. The highest ranking an esper could achieve. Tsuchimikado's level 5 ability, Auto Rebirth, gave him a from of agelessness, indestructibility, and high-speed regeneration when all else failed. This was due to the speed at which his aim field caused his cells to generate and regrow, enhancing his physical durability and endurance.

In shorter terms, for all intents and purposes. Tsuchimikado was immortal. ]