After 1 month of training, three girls have become very strong with a rich battle experience (that came from constantly fighting with Haruto). In this 1 month, Haruto has given them books on different techniques like he has given a knife technique to Toru, a fist technique to Mina and a rod/pole technique to Momo from the Library of Heaven path with no flaw.
He also gave them three strength-enhancing fruit to the three girls which further increased their strength. Based on their strength their strength should be equal to a Low-level Hero and along with all the techniques they should be around Mid Level Hero but Haruto told them to not show this infront of others until they reached the standards of High Level Hero or A rank Heroes.
During this one month, he also began to search for 'chi' control technique, he read them all and compiled them to a chi control technique with no flaws. He also learns that there are many correlations between 'chi' and 'nen' from Hunter x Hunter world.
He thought that if he could learn or perfect 'chi' then he could develop 'nen' on his own which will give him a huge boost when he will go to other worlds for adventure. He also plan to think of a way to learn Haki but he decided to do that after he completely masters 'nen'.
He gave the 'Chi' Control Technique to his parents and the three girls saying that it will increase their strength and they no longer need to use the Nameless breathing Technique. 'Chi' Control Technique is a way to control the life force of the body, it could strengthen the body, amplify the attack and many more. He also told them the benefit as mastering the technique will give them an increase in lifespan and regain youth for a little longer time.
Hearing this his mother and the three girls began training very seriously which dumbfounded him and his father who just smiled wryly. It took them some time but they got a hang of it and they learned it easily with the help of Haruto. Another thing notable is that their appetite increased a lot as training life force techniques drained them a lot than normal training.
In the last month, whenever he goes to Realm of Violet Jade Immortal, he didn't train as he did previously, he increased the gravity of the gravity suit but he just mastered the 'chi' control technique and tried to find 'nen' nodes or aura nodes in his body. It took him for a while but he managed to find it and release it. It took him only a week to completely master 'nen' (which his more than 50 days if we calculate the time spent on the Realm of Violet Jade Immortal) with his instant mastery skill.
It should be noted that It took Netero years and years to learn 'nen' through enlightenment and many more years to completely master it. After mastering nen and all of its techniques he called his parents and the three girls to open their 'nen' nodes.
The moment their nen nodes opened they felt strangely powerful. Then Haruto taught them the basic Ten, Zetsu, Ren, and Hatsu and explained about it thoroughly and told them not to tell anyone about it.
With the Chi Control Technique or which can now be called a Nen Control Technique, it becomes easier for them to train.
[Ten- is the process of keeping the nodes open, but also having aura flow through and around the body rather than away from it. Once maintained, it creates a shroud around the user that feels similar to standing in a lukewarm, viscous fluid. Ten maintains youthful vigor and reduces one's aging. Ten is the most basic defense against emotional Nen attacks, and it also offers limited protection against physical attacks, but hardly any when said attacks are enhanced with aura.
Zetsu- It stops the flow of aura from their body altogether. By closing all of their Aura Nodes, the user is able to halt all outflow of their aura like water from a valve, making their presence much harder or even impossible to sense. It can also be used to relieve fatigue since it forces the body's external layer of aura to be fully contained within.
Ren- focuses on outputting a larger amount of aura than Ten, projecting it outwards explosively. This amplifies the user's physical strength and durability. One can train their Ren to extend its duration and increase the amount of aura at their disposal.
Hatsu- Hatsu is one's personal expression of Nen. Its qualities are influenced by but not restricted to the Nen user's natural Nen category, one of the six available. It is used to project one's aura to carry out a certain function, creating a special and unique paranormal ability.
Other are advanced techniques which utilize a combination of all these basic techniques like In, En, Ko, Ken, Shu, Ryu, etc]
If we divide nen mastery into levels, beginner His parents were at the basic level and the three girls were at the intermediate level after 2 weeks of training which is very surprising for him. Haruto estimated that it will only take them 2-3 years to reach the complete level, "They are geniuses". Today, Haruto was sitting inside the Realm of Violet Jade Immortal after practicing his sword Techniques in high gravity and using Nen to envelop the sword (which is called Shu). He began planning for the future. He thought, "My parents are now very strong so when I travel, I don't have to worry about them and I will try to eliminate League of Villains as soon as possible. I think I will capture Tomura and others and torture him to get the location of All for one and other high-level ones to not create future problems for my family. After which I will go to Hunter X Hunter world, 3 years before Gon and Killua begin their Hunter exam. In that time I will go to Dark Continent to train myself and enjoy thereafter some time and move onto the next World". In HunterXHunter, Kite's En was about 50 meters wide, Zeno Zoldyck's En was about 300 meters wide and Neferpitou's En was about 2km. Haruto used them as a parameter. He found that his En covers up to a distance of 20km (due to his huge lifeforce). Then he quickly removed all the thoughts from his head and called the three girls. They came towards him and asked. Toru/Momo/Mina – What happened Haru? Haruto – Nothing, you stop your training for now and go to sleep as tomorrow we will go on a date. Toru - "blushing" dadada....Date? Momo – Yahoooo. We will watch movies and go shopping tomorrow. Mina – We will do many naughty things. Haruto when heard what Mina said, also blushed a little as he was a virgin in his previous life but then said, "Yes, we will go shopping, watch movies and many more". Looking at Mina and other girls' ass he slowly said, "We will also do some naughty things". Hearing this Toru fainted, Momo blushed while Mina hugged him. After that, they went to rest and prepare for tomorrow. Haruto also went to sleep and began planning what will he do on a date. It's not like he didn't have any girlfriend in his past life. He had dated an otaku girl like him but they didn't go any more than kissing so he died as a virgin. And in dating, they mostly watched and discussed their favorite animes and nothing more. So tomorrow will be a new experience for him. Thinking like that, he went to sleep….