To withstand future invasions by enemies from the Ōtsutsuki Main Family, they had to grow stronger.
Chinatsu needed to improve her strength again, and so did Naruto and Sasuke. Neither of them could stand by when she was in danger. Even if all they could do was support her from the sidelines, they would step forward without hesitation. Even that was better than hiding behind their older sister and letting her protect them.
And if the Ōtsutsuki Main Family really came, the danger would rise to another level. As they were now, Naruto and Sasuke might not even qualify to provide support.
Momoshiki's and Isshiki's "Karma" offered them that opportunity.
The Uzumaki Clan and the Uchiha Clan were already offshoots of the Otsutsuki bloodline. Even if their blood became purely Otsutsuki now, it would hardly mean abandoning their ancestors. After all, their ancestors were Otsutsuki.
Hearing Chinatsu's explanation, Naruto breathed a sigh of relief. He now knew that the tattoo on his body probably posed no major risk.
Sasuke, meanwhile, turned toward Isshiki as Chinatsu spoke. In just a few minutes, Isshiki would crumble into dust and die for good.
Momoshiki had already implanted his Karma. Only Isshiki's remained.
Sasuke: "So, are you giving it to me?"
Isshiki: "Uh, well..."
For Isshiki, whether he gave it away would make little difference to his situation. Chinatsu would never give him a chance to take over Sasuke's body anyway.
Giving it to him offered no benefit.
But then again, refusing offered no benefit either.
With only a few minutes of life remaining, Isshiki spent several seconds considering the matter. In the end, he chose to hand over his "Karma."
To Isshiki, leaving behind even just his power was slightly better than vanishing without a trace. At least it would serve as proof