Ancient Dragon in Arknights

"Name?"
"Nesario".
"age?"
"Twenty-two years old."
"Race?"
“Vaivan”.
"Are you sure?" (What?! Vayvan's heart is like fire?!)
"determine."
"Um... what position do you plan to take?"
"Tachi."
"Excuse me, what position does 'Tachi' refer to?"
"Huh? You don't have a katana? Dual swords will do."
"...I heard you graduated from the Royal Guard Academy of Victoria, is that right? How about giving it a try?"
"Alright, then let's go with the Guards."
Saria has a younger brother, and even someone as hard as a diamond like her gets a headache just thinking about him. This kid is a good-for-nothing who flirts with girls all day long and constantly asks her for money. Rhine Lab isn't her personal property!
I heard he made a fortune in Lentinium and even started refusing to go home. For such a rebellious younger brother, only a firm hand can teach him a lesson.
(This is the story of a Vyvan who evolves on the continent of Terra and eventually grows into an Elder Dragon.)