Burnout
Summary: Mugetsu is both more and less damaging than the Kurosaki men believe.
Disclaimer: The Laughing Phoenix does not own Bleach. This is the product of a brainwave after a particularly grueling week.
Isshin thought he knew exactly what he was getting into with Mugetsu. The technique had come up in a training session with Engetsu shortly after he'd been named Captain, and it had taken him the better part of a year to get his Zanpakuto to divulge the details. He'd been suitably impressed.
The ultimate last-resort weapon. A single wave of hyper-destructive energy, deployed in a manner akin to a suicide strike. But instead of taking his life, it would take his powers, his abilities as a Shinigami.
Engetsu had made him swear forwards, backwards, upside-down and sideways that he'd never, ever use it. Not unless the Universe was falling down around their ears. As fascinating as he found the technique, Isshin was only too happy to agree.
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It had been an accident. He'd been settled into Urahara's gigai for less than a week before a powerful hollow attacked. Masaki, who could see the beast, was trapped against the rubble from a building it had knocked down, while Isshin was fighting his way over a pile of cracked concrete slabs and twisted metal on the creature's other side.
The creature was raising its claws, preparing to pounce and destroy the one woman who made Isshin feel like life was worth living, when the ex-Captain lost it. He felt for the space in his mind where Engetsu's powers were, reached, and pulled in the way he'd been taught to do so many years previously.
Isshin managed to overload the gigai and free himself from it momentarily. However, he overpowered the attack he'd planned to use and before he could stop himself Mugetsu was searing the Hollow into oblivion, the great black wave rising into the sky as it dissipated.
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Masaki was safe, but Engetsu was gone. It was…odd, Isshin decided, like trying to stretch only to find you were missing an essential part of yourself. He wondered briefly if this was what psychologists were talking about when they mentioned phantom limbs, but pushed it away. There was nothing he could do about it now.
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The night after Masaki's funeral, a neighbor took the half-asleep Kurosaki children to spend the night at her house. "To give you some time alone," she said, eyeing Isshin carefully.
With the children out of the house, the place became silent. Unable to stand the pervasive quiet, Isshin pulled out a bottle of sake.
And another.
And the bottle of whisky Ryuuken had given him at his wedding.
Before long, Isshin was completely drunk, having passed inebriation with barely a wave and forging on towards insensibility. He was about to take another swig out of the bottle in front of him (was it still the whisky? He couldn't remember and the bottles wouldn't hold still to let him count them) when a voice roared in his ear.
"WHAT IN THE NAME OF HELL DO YOU THINK YOU'RE DOING?"
Isshin coughed and choked, sputtering as the alcohol burned its way down the wrong pipe. He spun wildly around, nearly falling over, but there was nobody behind him.
"Of course not, lackwit!" The voice snarled. "I'm inside your head, remember?"
That was a voice Isshin had never thought he'd hear again. "Engetsu?"
"Who else, you utter waste of space!" the Zanpakuto snapped. "And I repeat: What in the name of hell do you think you're doing?"
"M'saki's dead, Engetsu," Isshin informed his Zanpakuto moodily, darkly, too despondent to even care that the manifestation of his inner self was back after so many years of being little more than a half-remembered dream. "She's dead, an' it's all my fault."
"Don't be stupid, Isshin, it makes you look like a moron." Engetsu informed him. "Oh, wait…"
"Yep." Isshin nodded, then had to wince as the room spun. "Tha's me. Moron."
There was a moment of silence. "Isshin," Engetsu said slowly, "You've had more than enough to drink. Put the bottle down."
"Nuh-uh." Isshin tried to cuddle the bottle to himself and ended up splashing a large amount of its contents down his front. "'S helping."
"Put it down Isshin. Getting blackout drunk isn't going to help you deal with this."
"Hurts too much."
"Gods all damn it, Isshin! You're hardly the first man to lose his wife to a Hollow attack! And what about the kids, did you think about them? They've already lost their mother, what do you think they would feel if they came back tomorrow to find their father had drunk himself to death?"
The words broke through. With a cry of rage and disgust Isshin threw the bottle away from him, letting it roll away to settle by the door, trailing a stream of golden-brown alcohol as it did so. He stared at it for a minute, then stared at his hands.
Gods. The kids. Sweet little Karin and Yuzu, and proud, protective little Ichigo. Isshin buried his face in his hands. What have I done?
Under the prodding and verbal abuse of Engetsu, Isshin cleaned himself and the mess up. He still had a hangover the next day, but at least he was alive. He went to get the kids from his neighbor the next day and spent a lot of time just looking at them, reminding himself that he lived for them, now.
The next years were difficult. Masaki's death had torn a great, gaping hole in Isshin, and even though he poured himself into his children, it still hurt. Some days were better than others, but he slowly started to heal, Engetsu providing metaphorical kicks in the pants as necessary.
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The big surprise was when his reiatsu started slowly coming back – deadened by the gigai, but unquestionably there. While he still wasn't combat-capable yet and wouldn't be for a while still, even if he'd been able to get out of Urahara's gigai on his own, it was enough to sense some of what was going on with Ichigo.
His son was an absolute powerhouse. Even more than he'd been. And it was frustrating to Isshin, because he still wasn't at a level where he could teach his son, and three short months before he got there a Shinigami appeared in town and triggered Ichigo's powers herself. He couldn't risk discovery, so Isshin kept his head down and tried to believe that Urahara and Yoruichi knew what they were doing.
Then Ichigo disappeared for a week and a half, leaving a mod-soul in his place. And when he got back…there was a strong, dark undertone to his powers that smelt of Hollow and his reiatsu moved in a way that screamed "Bankai capable!" to Isshin. When he confronted Urahara, he'd been sat down and given a quick history lesson, then brought up to speed on Soul Society's current struggles.
It was big. Far bigger than he'd thought, than he'd dreamed, and he nearly choked on his fear for his children, particularly Ichigo, who was caught up in it already. And so Isshin quietly took time to train with Engetsu again, to bring himself back up to the level he'd once claimed.
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Isshin was never so proud of Ichigo as the day he used Mugetsu to bring down Aizen. To use that kind of attack, knowing exactly what it would do to you, knowing that it would strip you of a large part of yourself, required a maturity that made Isshin smile, secure in the knowledge that his little boy was growing up to be a good man.
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Mugetsu is as destructive as it is because it is effectively a brute-force conversion of the entirety of the Shinigami's spiritual energy. As such, it requires a Shinigami with correspondingly high levels of reiatsu, as they're the only ones who can survive without the forces involved ripping them apart, let alone making it worthwhile.
It does not, however, destroy their ability to sense, channel, and utilize reiatsu completely.
Instead, it rips out the reiatsu, damaging the usual mechanisms and forcing whatever little energy remains into ensuring the simple survival of the user. For a long time, the Shinigami's reiatsu is focused on maintaining the Shinigami's health and repairing the damage – only then can it start to fill up the reserves again. It's a long, arduous process that takes time. It took Isshin fourteen years to begin to hear Engetsu again, and it was twenty before he was back to his previous battle strength. However, he will never be able to use Mugetsu again: he may have healed, but he is not what he was before it and another use will kill him.
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In the odd between-world where the Zanpakuto reside, two figures stood side by side on the edge of a building. Engetsu chuckled as he glanced sideways at the translucent figure of Zangetsu. "Good to see you again as more than just heat-haze."
Zangetsu ignored the quip. "Ichigo's powers are returning," he said calmly, lifting a hand to watch the faded scenery through it. "Far more quickly than anticipated, given previous users of Mugetsu." he added.
Engetsu ignored the implied dig at his own Shinigami. "It's been what, a year and a half now? I'd say another two years or so and you'll be able to talk to him again."
Shrugging slightly, Zangetsu dropped his hand. "Perhaps. Listening has never been Ichigo's strong point."
There was a sudden, faint thunk and a strong rush of wind. "If Tachikaze and Kazeshini have been fighting again, I swear I'm going to go find Kubikiri Orochi and Tobiume and see if we can't find them something to do." Engetsu muttered, brushing dust out of his eyes. "Like sticking them in a deep hole somewhere." Movement to his right had him turning to look at his companion. Zangetsu was staring down at himself, looking far more solid than he had any right to be.
"Well now…that's interesting."
A/N: This is what happens when I'm overtired. Plot bunnies like this write themselves.
Thank you to Rusting Roses for convincing me that I wasn't completely insane when I came up with this, and for the superb beta-work.
Thoughts? Comments? We know squat about Mugetsu, I'd like to hear what you've come up with.