Disclaimer: I do not own Gintama nor its characters. All rights belong to Sorachi Hideaki.
For years, he has had one less back to protect. After this fight, he will have one less head to cut down.
He had countless chances to kill him since he realized something was wrong with him and there was no turning back. But he always believed there was a chance to help him. He didn't want to hurt him. Because he promised his sensei he will protect his comrades. And he was a comrade, wasn't he?
He thought of him as a comrade. He wanted to believe he was still his comrade. He believed that (probably fooled himself) there was still a chance for him. But when he sabotaged that festival he became aware of his illusion. He stopped thinking him as a comrade when he hurt his friends and sold them to pirates.
He has to be killed. He thinks to himself. He hurt his friends. His friends are going to suffer even more if that man lives. He can see the evil spark in his green eye. But for some reason it is really hard to attack him.
It's probably because that green eye is the same one that had a innocent look years ago.
He can finally bring himself to attack his opponent. As he runs to slay him he realizes that for years he has had one less back to protect. After this fight, he will have one less head to cut.
Sensei is probably watching us. He thinks and the thought hurts. He nearly says that but it is too late for childish talk.
The victory goes to the white demon and his opponent falls.
For a brief second, he thinls he sees regret and pain in the green eyes as their light is fading. Probably an illusion.
He makes a grave for him. Even though he was an enemy, he was also an ex-comrade and a formidable opponent. The dead man's organisation probably made a better one for him but he doesn't care. He places the grave near the monument of his sensei with the help of an old friend.
After that he tries to live on like nothing has ever happened. He turns a blind eye to people celebrating a terrorist's death. He walks past the yakult on the markets. But sometimes his memories are triggered by the smallest things (a green eye, a bottle of yakult, an eye-bandage, a noble swordsman) and he feels like he is still around, sometimes he even looks around, tries to find him. Then he remembers.
Sometimes he wakes up from nightmares in the middle of night. He doesn't know how to handle them. Sometimes he just goes back to sleep, sometimes watches the stars with silent tears streaming down his face. (He once looked for an open shop to buy a yakult. There was not a particular reason. He just felt like drinking it. He then bought some more and hid it in case he wants to drink it another time.)
I'll get over it with time, he thought. But he was not really sure this was kind of a scar that completely heals with time.
A/N: Thank you for reading! I know "green" doesn't have any relation to the story I just couldn't find anything so went with green, because it is the colour of his eyes.