New Experiment
It is said the more one hurts others, the easier it becomes because one closes themself off from others. But people also close themselves off because they can't stand to be hurt by others anymore. Sometimes, one closes themself off because emotions are weaknesses that could be exploited. There were plenty of reasons to close off one's emotions. Mask swore that he wouldn't let himself be affected by emotions and form attachments. He expected himself to keep that promise. The former Hokage shouldn't have any problems with something so simple.
How did he end up caring about the wellbeing of this child? No-- the boy has a name. The child is named Yota. How did he end up caring about Yota? When did he start caring? How could he have let this happen? Mask did not know. For such an intelligent man, he could be such an idiot.
Yota was not like ordinary children, he was gifted with a kekkai genkai and great potential to be a shinobi. He loved to play and run around like other children. But unlike other children, he was born frail and he exhausted himself easily. Yota was a sickly child. The boy probably wouldn't make it to the age of ten, let alone adulthood if his condition was left alone. It was a tragedy that the child's potential wouldn't be realized. But that was how the world worked, it wasn't fair but that's how things were.
Unless, he could change that. Tobirama could probably cure the condition all together, he was the man who brought the dead back to life after all. But should he bother? He could easily just keep the boy alive with the most basic treatments and not do anything about the condition. If he wanted to fix the condition, he would probably have to do experimental treatments that could be painful, and he would rather not do that sort of testing on a child.
Yota was frightened of him when they both met for the first time. That had been sometime before the Third Shinobi War. The boy was about four or five years old. The mask Tobirama wore scared the child, but that wasn't something he could help. The best he could do is convince Yota that he wasn't a monster or any kind of threat. He would need the boy's trust if he wanted to help the boy and fix the boy's condition. Mask could easily use his Sharingan to coerce the child into trusting him but that would be wrong, he needed to do this without mind tricks. It wouldn't be right to use his Sharingan on a child like that, he still had some degree of morality left. That aside, Tobirama felt bad for the child, because Yota was worse off than he was in his own childhood. That's probably a huge part of the decision to do what he could to cure Yota.
So that's why he decided to do something unexpected. Tobirama knelt down to the child so that they could be face to face. There was no one but them in the room that was repurposed into an examination room. Yota flinched back instinctively and made his fear of the masked man more apparent. Tobirama already knew the child was afraid of him, so that wasn't much of a surprise. The former Hokage carefully removed his mask so that Yota could see his face. This would help the boy trust him as Yota would have a face to associate him with instead of the mask that caused so much distress. It was fine for Yota to see his face, the boy was too young to know who he was and was unlikely to have visited the Hidden Leaf before.
"It's alright.. I'm not a monster or anything like that, I have a face like you." Tobirama said carefully to avoid making the child fear him even more.
The child hesitated before reaching for Tobirama's face. That was fine, Tobirama could allow this. Yota patted the former Hokage's face, as if to confirm that this was indeed a real face and not any sort of deception. The boy grinned when he found that the face was indeed legitimate, he wasn't afraid of the unmasked shinobi as he had been before. Tobirama gave a small smile, slightly amused by Yota's actions. It almost reminded him of Hashirama's children when they were smaller. Almost. He shouldn't be comparing this boy to Hashirama's children but he had no other children to compare him to apart from his brothers and perhaps his students, but he didn't deal with his students when they were this young.
He wanted to have children of his own once upon a time.
But that is a memory of another time in what he considers another life. There is no use for Mask to continue dwelling on that.
He would do everything in his power to help Yota, he could at least make sure this child would live a decent life. Tobirama could promise that at least, even if he shouldn't be making promises. But SHE would want him to be a better person, or at least try to be... helping Yota means he was trying to be a good person to some degree. Tobirama would be doing a good thing, plus with Yota's condition, he could talk himself into thinking he's doing this as a sort of side experiment.
Tobirama wasn't attached to the child, no, he swore off emotional attachments. Yota is an experiment, an excuse to play god... or at least that's what he tells himself. If the experimental treatments go well, the former Hokage would have a new student to train, a new shinobi to help keep others away from his place. Plus, this gave the former Hokage a new kekkai genkai to study should Yota survive and become his student. He definitely didn't consider the boy to be like a son to him. The boy is an experiment, or at least that's what Tobirama keeps telling himself. It's amazing how easily the former Hokage believes the lies he tells himself.
'Mask' certainly doesn't care when Yota imitates him in childish ways. He certainly doesn't smile beneath his wooden false face when the boy makes a childish mask and wears it around. The former Hokage certainly doesn't feel a hint of pride whenever the child tells him about his mask like he didn't notice that the child was wearing one. The boy was an experiment, nothing more. This was for science and as a scientist, 'Mask' wanted to study the Yota's kekkai genkai. Therefore, 'Mask' needed the child to live and for the child to live and use his kekkai genkai, the scientist would need to do something about that condition of fatigue and frailty. There's no room for personal attachments in scientific study.