I Grew Up with Red Dragon Sisters

He was reborn as a red dragon and grew up with his four sisters. Besides, he had an unreliable mom who espoused Spartan education.
Because of the betrayal of his family in his previous life, Neigher told himself that he would never trust anyone in this life.
However, as the elder brother, Neigher, who held firm to the principles of egotism, had never thought that he would become a "father" in this new family.
Since then, he had been set up by his dragon sisters.
…
One day, his mom suddenly told him that they would separate from each other.
"Humans are going to kill us all. We are the last giant dragons."
(This novel is healing and describes characters vividly. There is a climax at the end of each scroll.)