Minato discovered a truth of the Naruto world: Rasengan is nearly the only shape manipulation!
When he tried to make his chakra piercing like a drill, it transformed into lightning.
When he tried to make it cutting like a sword, it transformed into wind.
When he tried to make it pressuring like a waterflood, it transformed into water.
When he tried to make it impacting like an impact, it transformed into earth.
When he tried to make it vibrating like a dildo, the high-speed vibration produced heat and transform the chakra into fire.
The only thing that chakra doesn't ȧssociate with an element is the swirling and grinding nature of the Rasengan.
When he tried to make it flat and rotating at high speed like Krilin's Kienzan, it didn't work. This one could be attributed to his lack of chakra control. Maybe one day he could produce some pure chakra beam like in DBZ, after all, if you can create a Rasengan, why not a Rasen-Kienzan-beam?
'My dream of the ultimate ninjutsu 'Rasengan Kienzan Drilling Flood Impact Vibrating Sword Beam' is more or less forfeited. It would mean adding 5 elements to three shape manipulation, nearly impossible...Just the Rasenshuriken was already super hard to make, let's not even speak about that. I don't want some half-assed jutsu like Naruto that require clone to make.
Minato already took three years to develop the Rasengan, how long will it take for me to create such Jutsu, ugh, forget about it. First I must reeducate my chakra'
Minato looked up to Mikoto and Tsume walking on water, while Kushina was still stuck on the tree walking exercise. There was a two months vacation from the academy, Mikoto and Tsume clans saw that they did some good progress on their own, so they allowed them to have some hours per day to do what they want, while the rest was spent on their clans' training.
Even if he doubts that they don't know of him, for the time being, nobody complained about anything.
If he was in a cultivation novel, the family of the girls would have harassed him to death, but here, it's like people don't even care about women. Mei and Anko, two Grade Antique Weapons beauties that finished fat because nobody tried to woo them...
What he doesn't know is that Mikoto's father and Tsume parents were furious when somebody said to them that their girls were kissed by a boy, even if it was on the cheek. There are only two reasons why they didn't say anything about it is. First, because he has the protection of the Hokage. And second, it's because they benefit from him, and the stronger they become, the better for the clan. And maybe if they gained his confidence, they could learn some secrets that will benefit their clans.
'It's better for me that way. But I doubt that this will continue. Fugaku will not yield Mikoto, she represents his chance to become a clan head. Well, he can come and try, he is not on my level anymore, and even the girls are catching up to him quickly thanks to their motivation to grow strong, unlike in the canon where they train only for the sake of training, without real goals.
Kushina wanted to become Hokage for the attention, she never really put any real heat in her training like now.'
He wanted to teach them the Rasengan for protection purpose, unfortunately, they don't have enough chakra to create one or control in Kushina's case. Even he can only create four normal size one for the time being before he runs out of chakra. Speaking of it, thanks to having the whole development process inside his head, he succeeded in only a few tries, without even needing the balls.
'But man, this Jutsu sure is underrated in the anime. When Naruto use it, it just blows back the enemy instead of destroying their insides as it should do. Even Kakashi's Chidori: in the flashback of his Anbu time, he pierced his enemy like paper. Later, when he became team 7 sensei, his amazing jutsu was transformed into a slapping jutsu'
Seeing that Mikoto and Tsume began to tire already, he sighed 'The downside of being young, all of us are Sakuras (small amount of chakra), Well...'
Looking at Kushina this time that was still going strong after all this time, he was pretty much amazed at the potential of a jinchuriki, it has only been some months since she became one but her chakra reserves were already catching up to him. 'But because she was not one since birth, her potential is smaller than Naruto, and she doesn't have Asura chakra too...'
'Let's not even talk about her horrible chakra control, that doesn't progress at all because each day her chakra grow a bit stronger' He was having a headache with that, only with Kage Bunshin will she be able to truly grow fast, but in the end, he doesn't want to risk it. Not only there is a high chance that she will finish brain-dead even with the Kyuubi healing her because of her stubbornness to catch up to him, but she is not nearly discreet as a normal human...So he is sure that the next day, all Konoha will learn that she knows of a B-rank ninjutsu.'
Sensing an unpleasant feeling with his Hyper Intuition, with multiple chakra signatures around the clearing where they were, he couldn't help but be a little annoyed. Thankfully his training, for the time being, is not sėnsɨtɨvė, but he can't even train his Rasengan outside his house. 'The downside of being in the light, I should truly speed up the creation of the Bloodline clones, if not, I will never be able to train all those magnificent abilities. A relaxed mind is needed when one learn, if I have to check my back each time, it would be truly annoying'
Annoyed by those pest presences, he grumbled a bit, but his annoyance flew away when he saw the three girls before him, panting of exhaustion but smiling brightly.
"Walking on water is truly a blast!" Exclaimed Tsume happily. Her clan only focus on her taijutsu, if not for Minato, she would have not learned such an amazing trick for a long time.
"You're so lucky, I wish I could do it too" Grumbled Kushina, still vexed that her chakra control doesn't go up, and she began to bicker with Tsume.
Looking at them, Mikoto sported an amused smile, she was never tired of their antics.
"You've changed Mikoto"
'Cute' Thought Minato, his heart skipping a beat. The true him hidden behind the cold exterior, in the end, is still pretty much childish, he never experienced love, and he considered himself still a kid when he is around those three girls, so he saw nothing wrong at liking them, and a shota can't be a lolicon. "Before Kushina came to Konoha, you would never have smiled so brightly in front of others, you even disliked the loudness and brashness of Tsume"
"Mh" Mikoto didn't deny it. Before, she was always trying to make her dad proud, even if it means to act like a true Uchiha, an attitude that she always disliked. Even now, she is still graceful like ever, but when with them, she lost the impassive exterior that she cultivated since small, because 'An Uchiha can't smile to those beneath them, basically everyone that does not have the Sharingan.'
Thinking of her father and clan, she couldn't help but be melancholic. Since the speech of Minato, she opened her eyes and observed all their reactions more carefully, and she truly began to saw through their true nature.
Startled at having her hand taken, she looked up to see Minato holding it. "Don't worry, I will protect you. I will not let you be used as a sacrificial lamb sent to be married for politics"
Seeing his sincere smile and filled with warmth from his declaration, her heart began to flutter.
Unfortunately, this feeling didn't last long before Minato explode from laughter "Haha, you believed I would say that. Baaaaaaka (Fool), if you can't even beat them by yourself go play the princess in distress card, maybe somebody will help you" Rolling on the floor, Minato held his stomach, aching from all the laughter. Imagining Mikoto go "Kyaa, save me, my prince", he began to cry tears of laughter.
Kushina and Tsume joined in "Princess Mikoto" "Save me Minato-sama!"
A vein popped out on the temple of Mikoto, and she lunged at Kushina and Tsume, knowing that she had no way to catch Minato. They began to roll around the ground mock fighting.
"Ah, it's been such a long time since I had such a good laugh" mumbled Minato, satisfied.
Sensing his heart hammering strongly, he couldn't help but smile contently, it has been such a long time since he has felt such warmth in him, hanging out with those three truly make him content, and wishing that it could last forever. Unfortunately, he knew that it was just a foolish dream, in this world of bloodshed, if he wants to create his paradise, he must grow stronger than anyone.