Takezo Kensei was the hero that inspired the young Hiro Nakamura to be a hero, Hiro was told stories about Takezo Kensei by his father and it was the young Hiro's favourite bed-side story...

At the end of season 1, Sylar threw Hiro into a building and Hiro teleports to avoid crashing into the building and dying, Hiro then ends up in a field where sees two japanese armies, Hiro realised that he had traveled back in time to 1671. Hiro then meets Takezo Kensei and he was revealed to be a fraud, drunk and a womaniser. It is actually Hiro that makes him into a hero, but when Adam/Takezo sees Hiro kissing his love interest he betrays Hiro, and looks to take over Japan with Whitebeard. Hiro believes him to be dead after he was caught in an explosion, despite Hiro's knowledge Takezo/Adam's power, cellular rapid regeneration/spontaneous regeration.

During this time, Adam/Takezo/Richard has ten wives, and battles a man with the power of duplication.

In the present time, Adam's name is tossed around by various people, and was revealed to be organizing the deaths of the Company founders. Adam is then revealed to be Takezo Kensei's alias, and has lived for 400 years because of his power. He escaped from Comany containment by convincing Peter that they were in a prison. He helps Peter regain his memories, and they both set out to destroy the virus. We soon find out that it's Adam's intent to release the virus on the world, as he tried before. Luckily, before he can be successful this time, Hiro teleports him to Japan and buries him alive.

Powers

Adam has the same power as Claire, cellular rapid regeneration/spontaneous regeneration. But we have seen the full extent of his power unlike Claire's, as his powers have allowed him to live for 400 years. It has also let him live through being shot by arrows and slitting his own wrists. The only way Adam can get killed is by a bullet right through the head of just some solid object in the head. However, if the object gets removed from his brain, he would regenerate again. The reason he will "die" when something is in his head is that as soon as something enters his brain, the brain would instantly stop working and will not regenerate anymore. If the object is removed from the brain, the brain would work again and regenerate instantly.