Heihachi is fighting against a monster named Ogre, who has transformed into his true form. Despite its overwhelming power, he succeeded in defeat it. After all, he's a Mishima, and a Mishima will always win against anything including a monster such as Ogre.
Taking one second to rest, he looked at the unconscious body of his grandson, Jin Kazama. Upon learning that he shared the same power as his late son Kazuya whom he killed 20 years ago, it's not hard for him to know who his father is. With interest, he trained this young lad for his fight against Ogre, whom he wanted revenge on for killing his mother, Jun. Judging by how it looked, Jin failed to defeat him, leaving Heihachi to fight the monster in his place. As he saw him disappearing into dust, he knew that his chance to create the youth formula is gone but that didn't mattered to him. That was a secondary goal in his life.
As for his primary goal in life...
After waiting out for five minutes, the Tekken Force came to pick them up as per orders. The helicopters flew away from the temple, ready to go back to Tokyo.
Inside one of the helicopters is Heihachi tending to the unconscious Jin. He wondered if this boy should have a future after this; perhaps he's not as bad as Kazuya himself. He may have used him as a pawn against Ogre, but his power intrigued him and even a tragedy like the death of his mother would not deter him into a better life himself. Perhaps he could lead a better life than his late father.
"Huh?" Heihachi noticed something is wrong with Jin. The young lad may be unconscious, but he started to see tattoos appearing on his forehead. This means he is starting to lose control of the cursed blood in his veins. Thinking back on how he had to kill his wife Kazumi for it as well as their son, he knew that Jin's time is up.
"Just like his father."
He knew that if Jin woke up with his curse out of control, it would be a massacre. It's a good thing he remembered his purpose in life: to rid the world of the Devil Gene. Wasting no time, Heihachi picked up the unconscious body and threw it off the helicopter leaving Jin to fall to the ground far above the air. Despite the act to finally be rid of the last being who wielded the Devil Gene, he couldn't help but feel sadness. This man was better than his own son, yet he had to kill him in order to end the curse that started from Kazumi. At least the Hachijos are gone now as far as he's concerned.
As far as Heihachi knows, there will be no more devils.
Author's Note: What do you think?