Despite already having a card equal to or even stronger than a spirit, Katsu still wanted to increase his strength, so other than sealing spirits, there is only one-way training.
Luckily, he had a yard, so he didn't have to teleport to find an abandoned place.
The other girl went shopping, so he has the day almost to himself.
After coming to this world, his training schedule has been reduced to almost nothing to accompany these girls.
Now that he started training again, he made it his priority to unlock another One Piece power, Busoshoku Haki
Different from Kenbunshoku Haki, Busoshoku Haki is also known as Armament Haki allows the user to use their own spiritual energy as armor to defend against attacks, as well as make their own attacks more potent. It can also be used to bypass elements on creatures. A person can apply the armament to a section of their body, over their entire body, or even imbue it onto their weapons.
Since he already unlocked Kenbunshoku Haki, Busoshoku Haki can potentially be unlocked if he uses it while training.
He created a human figure made of ice and started using it to practice while using gravity magic to increase him to 7 times the normal gravity. He didn't dare increase anymore since this is his limit; his body is not a Saiyan, so if he reaches 10 times, he might really die. This way, his body can be continuously under pressure for it to be easier to unlock.
He wears a blindfold and activates his ability Kenbunshoku Haki and lets his puppet go into auto mode.
Despite losing the ability to see, he can still sense the presence of his puppet, so the moment it raises its fist against him, he also attacks, but because he is not using magic to enhance his hand and is being pressed by gravity, his fist is extremely weak. Once the two collide, Katsu feels like his hand punched a metal object, which is very painful, but he has to tolerate the pain and continue.
The human puppet quickly positions itself in another location and attacks him.
His training continues for hours as he tries to touch the feeling of activating Haki, even going so far as to create more creatures to attack him.
He accumulates a lot of bruises, but slowly the coating on his arm turns black. Hardening is the most basic application of Busoshoku Haki is the black coating on his arms, but it quickly fades, and it is very unstable, like a ghost constantly hopping between reality and a dream.
Hours of training are slowly increasing the duration of his skills from 1 second to almost 30 seconds. The elemental creatures he created can't survive his attack when Hardening, so he started using his cards to practice.
He summoned Kaiser Vorse Raider and Revival Jam. The two of them have their own intelligence, so their attack is much more deadly than those brainless ice creatures.
Revival Jam can move very fast in its liquid form and change its structure quickly to dodge his strike. When he attacks, he can only feel the empty air around his fist while Kaiser Vorse Raider uses his axe bears to defend and attack him. Obviously, he didn't dare meet his weapon head-on, so he can only try to avoid it and occasionally wave a few fists in its direction.
His cards have a loyal setting, so they will control their strength so as not to kill him, but that doesn't mean they will go easy on him. The deep cut and pain inflicted on him are also part of his experience training his Haki, and the pain can simulate his body's adaptation.
When the girls return, he already lies on the ground with many cuts and bruises on his body.
They almost thought that someone ambushed him and became alert to look around for the culprit, but in the end, they found nothing, so they could only move him into the house for healing.
After he wakes up, they finally understand everything.
"Master really is too reckless," Mana said pouting her lips and staring at him angrily, pinching Katsu's cheek.
His body hasn't completely recovered, so Mana's pinch is very painful for him, but luckily, Mana only wanted to teach him a lesson, so she stopped after a while.
"I will be more careful next time," he said embarrassingly, knowing he had caused them to worry about him.
At least he finally mastered hardening so he could use it in battle and his Haki six sense also increase so next time if a sniper shot at him he can react in time.