Even though she wasn't directly able to affect Luna as she clad herself in her haki, it affected Luna's fighting power. Since she had to stay vigilant all the time in fear of getting affected by the devil fruit powers of Ain.
Her return-return fruit was able to turn everything she touches into certain years in the past.
Since they were fighting on the Island with a lot of building and mountains, it severed as a great advantage to her.
Even so, Ain wasn't able to defeat Luna. Luna has extraordinary physical strength and stamina, much greater than Ain's but she can't keep fighting and using her haki to the longest time since she was only at Colored haki stage.
If not for Nuke's words, 'Not to use her devil fruit powers' she would be easily able to defeat Ain.
She also knows it's to temper their haki and reaches the next stage. Like Nuke said, her haki is showing the ability to reach a perfect stage.
Both Nuke and Luna want their haki to be mighty, flawless and long-lasting. This also the reason they suppressed their Haki in reaching the next stage- Advanced Stage.
Nuke plan is to drain and tire out his haki to absolute end and then advance it to the next level.
Clearly, When one reaches a limit their strength will improve. Same as that, when his haki reaches the limit in suppressed stage, his haki will improve.
Once he has done that, he can advance his haki to the next level.
"Haha, brat you talked big but you are not any showing progress in beating me. Are you only capable of talking crap?" Shuzo laughed and spoke.
Nuke didn't reply, he continued fighting while he deliberately used a large amount of haki. Both of their fights lasted for four hours and it looked like it won't stop anytime soon.
Finally, Nuke was sent flying by a powerful punch of Shuzo while his haki also fully exhausted.
'Now's should be a perfect time to advance the haki, since Luna is also in a similar state as me.' Nuke pondered.
"Luna, Let's do it." Nuke yelled.
"I was waiting for it" Luna replied.
'What are they doing? They should have exhausted their haki to their limit... Do they have other trump cards?' Both Shuzo and Ain was confused by sudden words of Nuke.
Purple air cracks began to form around Nuke and Luna, as Haki in their body become Violent and Fierce. A large 'boom' echoed and everything around Nuke and Luna blasted away.
Finally, their Haki advanced to the Next stage- Advanced 'General' Level.
Both of them could feel a boundless haki in their body, and their strength reached a new level.
Name: Nuke Gray
Constitution: 9-(Star Body: 340)
Ability: Origin Star Body Technique. [Stage 1: Advanced]
Haki: [Observation Haki: 310][Armament Haki: 330]
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