After Kasumi gave birth, Kenshin immediately received a level-up notification. He decided to invest the free skill point into the "Formation Creation" skill, raising it to the fifth level, first sitting comfortably to digest the received information, and immediately felt mental fatigue.
There was so much new knowledge that even his quite strong mind couldn't digest it in half a minute. To his surprise, there wasn't much practical knowledge among the new information, but theoretical knowledge was enormous.
This reminded him of high school chemistry lessons. When expectations of incredibly fascinating chemical experiments crashed against the harsh reality of studying valency and chirality.
Having fully digested the received information and rested a bit, Kenshin quite quickly came up with how to add some durability to the exo-suit, and an idea was born in his mind about a possible way to detect psionic energy.
Instantly jumping to his feet, to the surprised looks of his two wives and two little sons, Kenshin rushed to his office so as not to lose inspiration.
*****
The next two weeks flew by unnoticed. The Nakayama family home was full of peace and tranquility. Kenshin worked, the girls took care of the children, older sons trained, and younger ones grew.
During this time many different events occurred. On the 206th day Kenshin impregnated Kasumi again, giving her a charge of joy for several days. The kunoichi from the Nara clan opened up to him from a new side. Such an authoritative and aggressive girl outside the family turned out to be an incredibly caring and gentle mother. Fifteenth was always surrounded by mom's care and grew in rays of love.
In the evening of the 208th day, Kenshin finally finished structuring the Nara clan's taijutsu and began gradually transferring this knowledge to his sons. Two per day, starting with Third and Ichiro.
On the 210th day Thirteenth and Fourteenth finally matured and were sent to the gym under the skillful guidance of older brothers. Fifteenth was terribly jealous of them and impatiently waited for when he could become as strong as the two older brothers he grew up with.
During this time the "Chakra Quality" indicator for almost all sons from Ichiro to Eighth jumped up. Ichiro finally reached Chakra Quality of 4 units, firmly stepping into Chunin rank. All others, thanks to concentrated blue sage tea, firmly established themselves at peak Genin rank. According to Kasumi's estimates, Aya's sons, thanks to their Sharingan, were practically not inferior to an average Chunin. Sons from Natsumi were a bit weaker but compensated with better control and chakra quantity.
Most of the day Kenshin spent in his office working on improving the exo-suit. During this time he achieved very big results. He finally figured out how to dissipate impulse without losing coordination. By this point the suit could dampen and dissipate impulse from a not-too-strong Chunin's blow. The exo-suit still couldn't fully dampen impulse from Kasumi's full-power strikes, so Kenshin could only go into deaf defense and crash body-first into walls and ceiling. These blows weren't fully dampened and felt like half-strength blows from an ordinary person, leaving bruises on the body. But even so, Kasumi was in complete shock from the possibilities of this exo-suit and regretted that the Nara clan didn't have such suits.
Besides joyful events, there were less joyful ones. Kenshin still couldn't catch psionic power. He tried many methods and under telekinesis pressure got only a slight hint that an unidentified energy was touching the formation node. No matter how he tried, the formation refused to capture this energy. Kenshin was a bit upset but decided he didn't have sufficient qualification in formations to conduct such outstanding research on detecting unknown energy.
In the evening of the 215th day Aya and Natsumi gave birth again, giving Kenshin a new level. Sixteenth and Seventeenth had a talent indicator of 23 units, setting a new record among children from the two wives.
After receiving the fourteenth level, Kenshin invested the free skill point into the "Create Refuge" ability, raising it to the fourth level. With the new ability level, finally all household members got access to the menu. Kenshin set several restrictions preventing underage children from mischief and also expanded his office, adding a separate room for a "workshop."
He also slightly expanded the gym and finally created a separate pool for his sons as well as their own dining hall. He decided to completely separate the "parent" and "children" wings, making them fully autonomous and comfortable for living. The number of possible residents in the refuge increased to a hundred, as did the amount of food available per day.
In addition, he slightly remodeled the sons' rooms, settling them two per room. Each lived with the brother he grew up with, except Ichiro. He lived alone, enjoying the position of commander and the most skilled of the sons.
By morning of the 218th day, Fifteenth finally became an adult and was assigned to the gym under Ichiro's personal training. At the moment he was the most talented and required particularly careful training.
In the evening of the 220th day, Kasumi gave birth to a baby named "Eighteenth," his talent indicator was slightly less than Fifteenth's but still an impressive 33 units. Kenshin was immensely glad for such excellent family addition and satisfied all desires of his new wife.
By lunch of the 221st day, Fifteenth under Ichiro's careful guidance finally awakened chakra and was immediately carefully examined by his impatient father.
Name: Fifteenth
Age: 20 years
Talent level: 36
Chakra quality: 3
Chakra quantity: 3400
Chakra control: 44%
Shadow Authority Lv. 1
*****
Seeing the characteristics of his son who had just awakened chakra, Kenshin was shocked. He immediately laughed joyfully and praised the "baby."
"Fifteenth, you're simply incredible! To have chakra quality of three units right from the start… You're very talented." Kenshin said with a smile and, seeing Fifteenth proudly square his shoulders, added: "But that's not enough for special treatment. You're still the youngest and must obey older brothers. Talent alone won't make you special. Only hard work and your personal qualities. Understood?"
"Yes, Father…" Fifteenth muttered ashamedly. Over the past few months Kenshin had increasingly gotten used to the role of family head and was incredibly strict with his sons. All younger sons nostalgically remembered their childhood when Father was gentle and loving, because after growing up he was incredibly strict.
"Good, you're free. Ichiro, let's have a spar." Kenshin declared, plunging Fifteenth into complete shock. Until this moment he was sure his father was an ordinary person with no combat power.
Ichiro silently nodded and followed to a special heavily reinforced room capable of withstanding a battle between two Chunin. Fifteenth quietly tagged along behind Father and older brother but was stopped.
"If you want to watch, watch through the window." Kenshin said calmly and entered.