I thought this would be in three parts but it'll probably keep going for a little longer.

Part One:

Mature Content

[GIF] Renewal Center - Age Regression [2/3] by Transviscera

Jason peered through the pod window and pressed the button for the intercom. "Knight to E3."
Now that his grandfather was awake and mobile, he'd been decanted out of the womb-like gestation tube into larger recovery tank. It was still submerged with nourishing, body-temperature goop, but had space to move around and was stocked with boardgames and light gym equipment to aid recuperation. His mental and motor functions had taken a beating, not just from the long decades of senescence. Even the cells of his brain had been replaced by the renewal, and things had been lost in the shuffle. Dusty old memories and disused skills were the first to go, and there was some minor aphasia.
Reginald gripped the knight clumsily, moving the magnetised piece with painstaking slowness across the board. He furrowed his pretty features in thought, delicate eyebrows scrunching together. "You... sunk my battleship?"
"It's just 'checkmate', grandpa," Jason said gently.
"Yes, yes, of course. Chessmate." Close enough. Reginald stared forlornly at the two claimed white pieces on his side of the board, and the larger black pile on his grandson's side. He huffed a stream of bubbles out of the respirator. "I remember when I could beat you at this."
"Well I was like five years old. It's just going to take time. You'll get there eventually, grandpa. Most people get years of training to prepare for renewal."
"Hmm, I was rather thrown in at the deep end, wasn't I? Thrown in? Is that the word? No. Pushed in," Reginald said pointedly, casting a dark look through the glass.
Jason winced. "You remember that?"
"It is the last thing I remember - you were trying to drown me."
"I wasn't trying to drown you! We were trying to save you," Jason said. I had no choice."
"Neither did I, apparently," Reginald replied curtly.
Things had been tense between him and his daughter since he awoke to find himself thrown into the body of a young body and his forged signature consenting to it. It hadn't been the jubilant awakening Jason had anticipated, no merry jig around the renewal tanks. In some ways, his grandfather was wearier now than he'd ever seemed as an old man, as if weighed down by the thought of the new life ahead of him.
Reginald packed away the chess set. Jason could see his annoyance growing every time he failed to fit a piece into the wrong-sized slot. A series of indignant tuts came through the intercom as he brute-forced the king into the slender slot for the queen.
"Everything okay, grandpa?"
"I just feel like an idiot. And I thought Asian women were supposed to be-"
"Grandpa!"
"Oh, I can't say that?" Reginald snapped back.
Kicking his long legs in the water, he rose, his short hair billowing around him as he swam to the shelf of boardgames, rummaging through them. A box of Scrabble, now his least-favourite game, was tossed over his shoulder at speed, leaking plastic pieces into the water. "There's no Molopony... Mopopoly- damnit... Monolopy..."
"The pieces are small. They probably didn't want you inhaling a hotel."
"Ah! Here we are! The Game of Life," Reginald said. He swam back and started setting up the board.
"Best of three?"
Reginald's eyes twinkled. "Oh no. You're just going to keep playing, again and again, until I give you permission to stop."