Kosu stood in awe, feeling the newfound power coursing through his veins. The power of the Dungeon's Heart had granted him a new technique that he had never seen before. He could feel it building up inside him, itching to be released. Jinpei was equally amazed at the power that Kosu had gained and was eager to research this new technique.

Kosu tested out his new ability, raising his katana and launching a slash at a nearby tree. The slash launched forward like a wave of energy, slicing through the trunk of the tree and causing it to topple over. Jinpei watched in amazement, taking notes and analyzing the energy waves that emanated from Kosu's attack.

Kosu was thrilled to have this new ability, but he knew that it was dangerous to wield such power without understanding it fully. He turned to Jinpei, seeking guidance on how to use this technique without causing harm to himself or others.

Jinpei was deep in thought, analyzing the data he had gathered so far. "This technique is unlike anything I've seen before," he said. "It's not domain magic, but it's not inner magic either. It's as if your mind is projecting your energy outward, creating a sort of telekinetic wave."

Kosu listened carefully, trying to understand the technicalities of his new ability. "So how do I control it?" he asked.

Jinpei thought for a moment before responding. "It seems that you need to focus your mind and your energy on a specific target. The more focused you are, the more powerful the Mind Slash will be."

Kosu nodded, understanding the importance of focus and control. He spent the next few days practicing his new technique, honing his skills and mastering the control over his energy.

As they continued to explore the Forbidden Dungeon, Kosu used his Mind Slash to defeat powerful monsters and clear the way forward. The technique proved to be a powerful tool in their journey, but it also raised more questions about the true nature of the Dungeon's Heart and the power it held.

Jinpei continued to research and analyze the Mind Slash, hoping to uncover its secrets and unlock the true potential of Kosu's newfound ability. But as they delved deeper into the heart of the dungeon, they knew that they were playing with fire. The power of the Dungeon's Heart was growing stronger, and they could feel its ominous presence lurking behind every corner.

Despite the danger, Kosu and Jinpei pressed forward, driven by their curiosity and their desire to uncover the secrets of the Forbidden Dungeon. But they knew that the road ahead would be treacherous, and that the power they had gained could be both a blessing and a curse.