It has been a few days, since Sans took in Eri inside of his house and helped her recover from the traumatic experience that Overhaul subjected her into. Eri, she never felt so happy in her life. She had been trapped with Overhaul for God knows how long it had been, and now, now because of Sans, she is finally free from him, and now has gained a positive outlook on her life. But it became more happier with what Sans has done for her. Due to signing an adopting form by some people, Eri has now been taken in as a new family member for the Gaster Family. Now being named to Eri Gaster, after Sans' surname and his father's surname, she is now the adoptive Younger Sister of Sans, and Eri looks up to Sans as the older brother. However, Sans also took it upon himself to help train her Quirk, Rewind, in order to not repeat the same thing that happened to her dad. While Eri was a little unsure about it at first, Sans tells her that they can test it on other stuff, such as Animals, bugs, or trees, just to avoid any unnecessary disappearances, since they will help Eri control better. Eri eventually agrees, and Sans began to help Eri with being able to control her powers.
When the others found out about her, they all adore her. However, while Atla does not adore her, she does treat her kindly, due to only seeing Sans as a big brother, rather than a love interest, which Atla does not seem to really mind. Bols' daughter, Logue, also gets along with Eri, and the 2 of them became friends, and it also helps that the both of them are at the same age of being six year old kids. Speaking of Bols, while Eri was a little scared of him at first, due to his appearance and the scary maid over his head, she eventually began to like him due to how kind Bols is. Cinder, the first and oldest adoptive sister, treats her in a sisterly way, with Team RWBY and JNPR simply noticing just how cute the girl is. Asia, Sheele, and Velvet have also taken a liking of Eri, due to their extremely kind personalities, just like Eri. Coco also seems to like Eri, but that could also be because of the clothing. This is the life that Eri had gotten, and it is the life that she had wanted to have, a family, looking over her, and caring for her well-being.
Sans smiled, as he finally gave a kid a second chance in life, and in all honesty...he is going to make sure that this second chance is not wasted, and will make sure that she does not regret it. And more importantly of all, he is going to make sure, that he will protect her from anything that tries to kill her.
He just hopes that it will be worth it at the end of the day
Meanwhile...
Outside, now in the city next to Ebott, Sans and Eri are at a forest of some kind, so Eri could practice her powers on it, as her powers can only affect living beings. So the trees count as being living. Now, Sans is trying to help her practice the speed of his much she rewinds a the state of a living being. Originally, she had trouble with trying to control the speed of how much she is rewinding on a target. But now, now she has some level of control over her powers, as she is slowing down the tree. Before, the target would be erased from existence when involving animals or small insects, as well as with trees. But as they continued with the training, she manage to slow it down to the point of simply turning them into their baby forms, or...turning a tree into its seed form.
Now, Eri's horn, which manage it grow to its original size again, began to glow yellow again, and than, the glow surrounds the tree, and began to shrunk it. Only...this time, it did not change into its seed form. No, instead, the tree shrunk until it became nothing more, than shrub. Looks like Sans' training is beginning to pay off for him, as Eri now has much more control over her Quirk than before.
After a little bit of practicing with a few other trees, Sans looks down at Eri with a smile present on his face, as he held her shoulder.
"Wow, Eri. You're clearly improving on your Quirk, after a few days. I'm proud of you."

YOU ARE READING
The Evolving Hero and the Ruler of the Abyss (Union Academy x Abyss Sans)
Action"I had thought...I had believed...I had hoped that...because you are heroes...you would care more about the lives of others, regardless of what and who they are, and that being heroes...you would care more about the people and the future that they l...