The entrance to the cave was a yawning maw in the side of a cliff, veiled by thick, magicule-saturated vines. Even from the outside, Astra felt the difference. The air was thick, heavy, not with gravity, but with a palpable, oppressive pressure. It was as if the very atmosphere had been condensed, each breath a conscious effort. His Magic Sense screamed with warnings; the density of energy here was orders of magnitude greater than in the forest.
[Ambient Magicule Density: Extreme. Caution advised for nascent Magicule users.]
"This is it!" Rimuru announced, his form seeming to glow brighter in the dim light of the cave entrance. "It's pretty intense in there. A really powerful... uh, presence, is sealed inside. But the antechamber should be safe! It's where I did a lot of my early evolving."
Astra nodded, his expression one of determined gratitude. "Thank you, Rimuru. This is perfect."
Stepping across the threshold was like pushing through an invisible, viscous wall. The pressure intensified, bearing down on his small frame not as weight, but as a force that sought to crush his spirit and snuff out his energy. It was a perfect simulation of high-gravity training, but with an added, spiritual dimension.
This was his new crucible.
He established a routine, a brutal schedule that would have broken any ordinary infant, Saiyan or otherwise.
Dawn: Ki and Mana Synergy.
He sat in a lotus position at the cave's mouth, where the pressure was strongest but still manageable. He focused on his breathing, drawing in the thick, magicule-rich air. He ran his Ki through his channels, feeling it burn with familiar, physical intensity. Then, he willed his new Magicule Breeder organ to activate, drawing the ambient energy in. At first, the two energies—the internal furnace of Ki and the external river of Mana—clashed, causing painful spasms. But Astra was a master of analysis and control.
Using [Stellar Forge], he didn't try to force them to merge. He analyzed their fundamental frequencies, their waveforms. He found a harmonic resonance. He began to cycle them not as opposing forces, but as two different instruments in the same orchestra. Ki fortified his cells, Mana insulated his channels. The result was a more resilient, more efficient energy system.
[Skill Developed: Energy Harmonization (Passive - Lv. 1)]
[Effect: Slight increase to total energy capacity and recovery rate. Reduces internal energy conflict.]
Midday: Physical Prowess.
He ventured deeper into the cave's antechamber, where the pressure was so thick it felt like wading through syrup. Here, he performed the most basic physical drills. Push-ups, squats, lunges. Every movement was a monumental effort, his muscles screaming, his bones feeling like they were grinding together. He pushed until his body collapsed, then used his minimal [Heal] spell to repair the micro-tears, only to begin again.
The Zenkai boosts came frequently, in small, steady increments. His Power Level, which had stagnated in the safe nursery, began to climb again.
[Power Level: 31 -> 37 -> 44 -> 52]
Each boost was followed by a session of [Energy Harmonization], solidifying the gains and integrating them with his growing mana pool.
Dusk: The Art of Destruction.
This was for his Saiyan instincts. He would lure one of the cave's inhabitants—a giant, magicule-hardened bat or a territorial rock lizard—into a fight. Their Power Levels were between 60 and 80, making them challenging but not insurmountable opponents.
He did not use the Jōgen Lance. That was a finishing move, a trump card. Instead, he honed his close-quarters combat. He used [Mind's Eye] to predict their movements, [Magic Sense] to feel the ebb and flow of their magical energy, and his enhanced physicality to deliver precise, crippling blows. He incorporated the basic magic he'd learned—a [Pebble Shot] to the eye to disorient, a localized [Wind Blade] to cut a tendon.
He fought with a cold, calculating fury that was entirely Kaito. There was no Saiyan joy in the battle, only the relentless pursuit of efficiency. He was not a warrior; he was a surgeon dissecting a problem.
After one such battle, where he defeated a Rock Lizard (Power Level 75) by shattering the joint of its primary leg with a Ki-infocused kick and then piercing its eye with a [Water Ball] compressed to needle-thinness, he received a new notification.
[Combat Style Synthesized. Would you like to formalize the fighting style?]
Astra reviewed the data. It was a style built on analysis, prediction, and minimal energy expenditure. It used the environment, used an opponent's momentum against them, and targeted critical weaknesses with surgical precision.
Yes, he mentally confirmed.
[Fighting Style Created: Void Fist (Lv. 1)]
[A style that seeks to create 'voids' in an opponent's defense and energy flow, ending conflicts with maximum efficiency. Integrates physical strikes, Ki, and basic magic.]
Weeks blended into a month of relentless training. Rimuru visited often, sometimes bringing strange fruits that boosted mana regeneration, other times just to chat. Astra played his part, the grateful, rapidly-growing infant, all the while secretly using [Stellar Forge] to analyze the slime's own ever-expanding repertoire of skills from a distance, building a vast library of magical data.
On the final day of his scheduled month, Astra stood in the center of the antechamber. The pressure that had once threatened to crush him was now a familiar embrace, a resistance that made him stronger with every breath. He looked at his status.
[User: Astra]
[Race: Named Saiyan (Otherworlder)]
[Power Level: 89]
[Magicule Capacity: 500/500]
[Skills: Void Fist (Lv. 2), Jōgen Lance (Lv. 2), Energy Harmonization (Lv. 3), Water Ball (Lv. 4), Wind Blade (Lv. 3), Heal (Lv. 2)...]
He had nearly tripled his Power Level. He was no longer the weakest being in the room. He had a foundation in a second energy system and a unique, synergistic fighting style.
The System chimed, its tone final for this world.
[Designated Time in World TS-001 (Slime) complete.]
[Initiating Return Protocol to Primary World: Dragon Ball.]
He turned to Rimuru, who had come to see him off.
"My time here is done," Astra projected. "I must return to my people. Thank you, Rimuru. For everything. I owe you a debt."
"Aww, you're leaving already?" Rimuru wobbled, saddened. "Well, take care of yourself, Astra! Come visit anytime! You'll always have a friend in Jura Forest!"
Astra gave a small, genuine nod. A friend. It was a resource more valuable than any skill.
As the emerald light of the forest began to dissolve around him, Astra felt the crushing pressure of the cave vanish, replaced by the familiar, heavy Ki of Planet Vegeta. He was returning. A single day had passed in the nursery.
But he was not the same infant who had left. He was Astra, the Named Saiyan. And he was ready to begin his true work.