Disclaimer: I don't own Gintama. This is my interpretation of the moment in episode 305/chapter 520. Warning: suicide discussion ahead.
Leaving behind conversation and laughter, for he would find no solace in the company of his faction tonight, Takasugi emerged out onto the main deck, which was coated in moonlight that rippled across the waves. Treading lightly, he moved toward the front of the vessel, away from the full moon with one eye gazing ahead, following his shadow.
Leagues away from the coast in the dead of night, the Kiheitai flagship drifted aimlessly, awaiting their Harusame allies, who weren't due to enter the earth's atmosphere for a few more hours. Once they arrived and regrouped with the rest of the Kiheitai fleet, they would ignite the start of a full-scale attack on the Bakufu with the goal of assassinating the current shogun.
With the nation teetering on the edge of a sword, now was the time for rumination, for doubts to creep in and undermine his resolve. But Takasugi had spent all the time in the world steeling himself to move forward. There was no reason to look back as he once did, wondering if this was the right path. It was the only path available to him.
Still, in moments like these, his longtime companion would come to him.
They were not a friend or lover or even an enemy, but they had been at Takasugi's side for countless years. As a result, they were more keenly aware of the inner turmoil that Takasugi refused to share with anyone else.
Stopping before the bow, Takasugi considered the comfort of his pipe, but when he sensed another presence, he decided to leave smoking for another time. Distractions of any kind were too loud and he needed to hear even the smallest voice calling from the depths. He craved whatever reassurance his companion could give him about what he ought to do, but his hatred for them ran deep into his core.
Unwilling to be caught off his guard, Takasugi decided he would initiate their conversation first. "I wish the moon would stay in hiding," he remarked, "It is too bright."
"It isn't the light that bothers you, it's the colour."
They understood that it was the colour of silver-white hair, cold pale skin, and death.
"Your eye burns."
"The other one hurts more," Takasugi answered with a sardonic curl of his mouth, "Isn't that ironic?" Ironic because the right eye continually forced him to witness the world marching toward a new era without him and his teacher. It was a persistent ache that no medicine could cure and occasionally dwarfed the pain of his left eye.
Yet, there was still something that hurt him more than anything else.
"Have you thought about what I said the last time we spoke?"
Takasugi closed his eye.
"I don't want to see you like this any longer."
Not now.
"I know what it feels like…knowing that those who have taken from me still live unaccounted for. It makes me angry every day, thinking of them."
Not now, damn you.
"Why do you torture yourself like this? You know there is an easier way."
Opening his eye, Takasugi glanced down at his shadowy form, stretching across the bow and losing itself over the edge. Then, it grew larger and darker, threatening to overtake the ship and souls within it.
"Why don't you avenge your teacher? You can put an end to everything by piercing your chest with a sword."
The shadow throbbed, and somewhere within, Takasugi could hear the taunting, the cursing, and the screaming that thrived on his rage and grief. Slipping a hand inside his kimono and placing it against his heart's region, he staggered under the weight of his companion's words and thought about how easily he could drown them out by killing them with his sword.
"Or perhaps you're waiting for him to do it."
Takasugi froze, right eye widening a fraction and left eye smoldering.
"No matter what you do, he will always be there to stop you – or save you."
He wanted to drive and twist that sword in deep, extinguish all remaining life force.
"But you don't need saving. You need justice. Vengeance. They are the same."
"Stop it," Takasugi hissed, clutching at his chest, fingernails digging into skin.
"Too many years have passed with you letting him live as he pleases. I wonder if he holds any remorse at all."
"Shut up…"
"After all, it's his fault your teacher is dead."
He clenched his teeth to halt the same questions he asked himself day in and day out to one whose name he uttered like a curse.
"You watched him do it."
Through the searing pain of his left eye, he saw a cliff's edge straight ahead, long strings of sandy grey hair matted with blood flying through the air, and a single tear rolling down a tormented face.
"He should suffer, as you do, but that will only hurt you more, won't it?"
"Shut up!"
Memories gave way to darkness, and Takasugi gradually became aware of his own ragged breaths and the ocean's murmurs. His arms were cold and heavy, as if from blood loss and strain, and he blinked several times to clear his vision.
He found that was holding his sword out in front of him, both hands gripping the handle with the blade pointing downward, poised to enter his abdomen.
"You should have died with him."
This time, Takasugi couldn't tell who had spoken.
He sheathed his sword and reached inside his kimono once more, trembling fingers enclosing around his pipe.
"Our blood…"
His right eye gazed at his shadow, forlorn.
"Or his…"
That single tear was a nightmare.
"And, maybe then, we will have rest."
Takasugi reached up to press a palm against his aching left eye and whispered, "Go to sleep, Beast."