All rights belong to Akira Toriyama, Toyotarou and Toei Animation
This is based on the manga cannon, so there may be some discrepancies with the anime.
Trunks had spent his week alternating between class, learning how to change a baby, which had most certainly not been pleasant (but had been told that girls were much easier because, unlike him, they didn't use their changer's face as target practice) and avoiding his persistent mother. She insisted on cornering him at every turn, trying to force him to watch a video of his father. Apparently he had a message for him.
But whatever it was, Trunks did not want to hear it. He didn't care if it was from the father he had once loved, the father who had cared for him with recalcitrance for the early years of his life, the father who, in later years, had supported him as he grew older.
That man was gone, would not be coming back. And good riddance, too. He was sick of being convinced of his value only to be shunted aside whenever a new threat arose, 'too young' to be of use. He was tired of his father leaving the planet for long stints at a time, missing all of Trunks' important milestones.
Was this what is was like to have fly-in-fly-out parents? Vegeta certainly treated fighting and training like a genuine occupation, which made sense since he had been a soldier. It irked the son, though, being left behind as his father soared to new heights, chased his dreams. Vegeta was free to come and go as he pleased, to leave them and return. At liberty to pursue his own goals, unburdened by a family.
Trunks resented that.
And he resented being thought of as an encumbrance.
For clearly he was, because his father had refused his advances to train with him. Had rebuffed his honest attempts to get to know the new Vegeta, to try to coax his father back from the depths of his own mind, as his mother had wanted.
Trunks didn't care about that now. He was no longer interested in training – it only held the importance that his father had placed on it, had been a way for them to bond while saving face, because Vegeta did not play with children. He wasn't driven to push himself physically like his father was; sure he liked exercise, but that back-breaking work? No way.
His half-saiyan pride was insufficient to tolerate the sorts of drills his father ran through.
That morning was the weekend, finally, after a long week filled with crying babies and weeping mothers, looking forlornly after their husbands. Apparently something had happened, apart from the recording, but Trunks didn't care what.
No matter what his mother said, however much she begged, he had given up on his father. Wanted nothing more to do with the man, and would be happy if he never saw him again.
Which was why he was so irritated when that very man disturbed his relaxing lie-in.
"Boy!" the man bellowed, slamming his fists against the door keeping the outside world away from a sleeping Trunks.
"Wha—?" Trunks mumbled, still half-in dream land, thinking of the strange flower costume his mother had been wearing as she shot the latest boss from his video game.
"Boy!" Vegeta repeated, causing Trunks to jerk, fully awake, sitting up in his bed.
"What you do want?!" he yelled at the woodwork, flinging back the covers to give his father a piece of his mind. His alarm clock told him it was 7:15 in the morning. Far too early on a weekend. Whatever his father was after, it could wait. For an eternity.
"Get dressed, boy, we are training in five minutes!"
What? Training? His father wanted to train with him? Months and months and a lifetime ago Trunks would have jumped at the opportunity, leaping on the balls of his feet at the acknowledgement. This Trunks, as it has already been established, was done.
"No, we are not."
"Yes we are! If you are not dressed and ready, out here, in five minutes, then I will drag you out to the gravity chamber in your pyjamas!"
"You can't kidnap me!" he protested, even as he rattled through his drawers, trying to find his training clothes. They had disappeared underneath a mountain of casual wear as they lay, disused, probably still stinking from the last time he had worn them and not bothered to wash.
"I am your father."
"You are not!"
"Don't take that tone with me, boy, or you will sorely regret it!"
Trunks didn't doubt that. He wasn't sure this was still the man who had refrained from sparring with him for fear of hurting him, since Vegeta struggled to hold back his strength in any battle-like situation. Wasn't used to needing to. He had still turned the gravity right up, though. He could certainly still do that, and it wasn't a pleasant sensation when you weren't used to it.
Hopping as he pulled his training shorts on, Trunks tried again to dissuade the man who was starting to act like a father again, in his own way.
"Come on, Dad, you don't really want to train me. I'm a disgrace to the saiyan race, remember?" That one had stung awfully, but he was going to use it to his advantage.
"Hmph. Perhaps, but only if you keep up your whining rather than training as you should. I can't believe you have let your body deteriorate to such a degree, even without me nagging you. That is a disgrace."
Trunks threw on a T-shirt hastily, aware of the minutes and seconds counting down. He heard Vegeta tell him he had a minute left as he was tying up his shoelaces.
"All right, I'm done!" he grouched, wrenching the door open to reveal his father, fist raised to assault the door one more time.
"Let's get this over with."
The older saiyan frowned at him, eyebrows drawn far down and eyes narrowing.
"A little more enthusiasm, if you please. The universe's greatest warrior is condescending to spend time training you, so you can silence your feeble protests."
"Huh?" Trunks played dumb, "Goku is here?"
This earned him a cuff around the ear, strong enough to send him a few steps forward, leaning over the floor as his mind reeled.
His father…his father had hit him.
Never, in all the years he had known him, had his father physically disciplined him. Even that one punch to the face when he had shown off his super saiyan transformation had been an accident, Trunks gathered.
He couldn't believe it.
"Dad…?" he questioned, because his world was shattering, as he realised he wasn't safe anymore. All of Vegeta's temper, all of his repressed violence and shouting had never been a true threat before, not really. He wouldn't actually hurt his son, would just find some other way to reprimand him.
So Trunks had been safe to let fly all of his worst words, his rage, the tempest roaring within his soul. Free to unleash everything he had as missiles against his father, words aimed to injure.
And Trunks had just realised how lucky he was that his father hadn't cared enough to properly discipline him. Because this man was unpredictable, could have hurt Trunks at any moment for his attitude.
Trunks felt sick with the dread of what could have been.
But he was also angry. Frightfully so. Because how dare his father cuff him over the ear? He was far too old for such treatment! And how dare he harm him at all?
Turning around to give his father a piece of his mind, because rage threw all caution to the wind in a saiyan and Trunks no longer cared about the risk, he stopped short.
His father was staring down at his hand like it was a worm.
Trunks decided to merely watch, to see what he would do. Vegeta flexed his fingers, examining his gloved palm and the back of his hand, seeming fascinated and disgusted at the same time, like it was a train wreck.
Eventually he shook it out, looking up to find Trunks regarding him with what he hoped was an innocent face.
"What are you looking at, boy?"
"Nothing."
Vegeta harrumphed, passing Trunks by hurriedly, calling for him to follow. He led his son outside, boots crunching over the morning dew as they made their way to the gravity room.
Dread and rage warred within Trunks, who was unsure which avenue to take. Should he vent his frustrations, or play it safe with the mercurial saiyan?
He decided the air on the side of caution, for now, as Vegeta opened the ominous door, motioning for him to enter.
An hour later and all of Trunks' calm was shot through. His father had started off full throttle, barely giving either of them a chance to warm up. He hadn't toned down his usual morning routine enough to cater for Trunks, who was sweating heavily within five minutes. He had collapsed after half an hour of various manoeuvres, unable to take any more, demanding a break for breakfast.
Vegeta had taken umbrage to that, deciding to only make things more difficult for Trunks. He had raised the gravity, declaring that he would raise it another 5Gs every time Trunks stopped, and ordered him to do push-ups.
The gravity was now up to 200Gs, and Trunks was ready to throw in the towel.
But he wasn't about to beg.
His exhaustion was only adding to his frustration, which had been building from the moment he had entered the torture chamber.
And he wasn't going to take any more, to Hell with caution. To Hell with the consequences, he was not a child anymore, he could take pain.
His arms buckled underneath him and he lay supine on the tiles, feeling their heat and vibrations through his aching muscles as Vegeta threatened him to rise.
"No, I'm done here," he answered, voice steady as he turned his face away.
"Get up, boy."
"I told you, I'm done," he winced as the gravity settings increased, but gave no outward sign of discomfort.
"We are not finished."
"Yes we are. We are done. You have trained me. Your duty has been fulfilled. Now let me go."
"We have not finished your training."
"So get on with yours, then!" Trunks bit out, finally facing the man and giving him his best glare, which only made his father smirk.
"No," he enunciated slowly.
Trunks couldn't keep it in anymore as the gravity rose yet again.
"Why?! Why are you doing this?! You've been pushing me away for months and now you want to train me?! Why?!"
"Because you have gotten weaker, and as your father it behoves me to arrest that decline."
"You haven't been interested in being a father at all until now! What—"
He faltered, the question of 'What's changed to make you so involved all of a sudden?' catching in his throat as he realised he already knew the answer.
He shouldn't have been upset, he really shouldn't have been. Not because such a realisation was not distressing for a child to hear, but because he shouldn't care about his father's approval anymore.
"Bra," he whispered, "It's Bra isn't it. That's why you're doing this. She's just been born and you've decided to be a parent again, even if you suck at it."
"Watch your language, boy," Vegeta warned, but Trunks was not finished. He forced himself onto his shaking legs, fists clenched so much as to pierce his flesh with his own fingernails.
"What am I to you? Am I not good enough for you?"
"What do you—?"
"I thought I was your child! And yet, it takes the arrival of my sister for you to see what's in front of you! Am I not good enough for you?!"
The man was listening; he had turned fully away from the control panel and was regarding him with a closed expression, hiding whatever he was feeling, if he was feeling anything.
"Am I your experiment?! Your trial period?! Gosh, she does nothing but cry, eat, and shit—"
"Language!"
"You don't get to scold me! It's clear to me who's the favourite child! For months and months you ignored all of my efforts to get through to you, you didn't care when I said you weren't my father, you didn't care one whit about me! And now you've decided to become a father, all because a miniscule lump has been projected out of Mum's –"
"Boy, that is enough!"
"I'M NOT DONE! WHY AM I NOT GOOD ENOUGH FOR YOU?!" He ascended to super saiyan in a peak of fury, emphasising his all-consuming rage. And disillusionment.
"Boy—"
"I HAVE A NAME!" Trunks screamed, aura whipping around him as he launched himself at the door.
"Let me out! LET ME OUT! I don't want to see you anymore!"
Vegeta didn't protest, didn't say a word. And Trunks didn't care to turn and see his expression as the lock gave a soft click, disengaging. No, Trunks didn't look back as he took to the sky in a furore, destination as far from home as possible.