(Okay, sorry for the cliche tsundere title...)
But as you may have guessed, this is our Tsundere-ish character! Her name is Rui, she's a second year at the same highschool where our main character, Yama, goes (by the way, Yama is a third year).
And because we, at Fallen Snow Studios, adore cliche and overused archetype, her relationship with the MC will be...
A childhood friend tsundere! We're genius, aren't we?
H-Hey! Come back! No! Don't quit this page yet!
...Okay, so a more original way to introduce my character you say?
Wait a minute...
*Diamonit goes looking for Rui*
Rui : Hey, what are you doing?!
Diamonit : Just introducing you. It's the first step to becoming famous!
Rui (blushing): H-Huh? Famous? I-I don't need this, as long as I'm with Yama, I'm fine...
Diamonit : Haha, you're so cute! But whether you want it or not, soon, males from all around the world will be able to witness your blushing face! Looking at your sprites with an amorous look, saying "Tsundere are the best!". Isn't that wonderful?!
Rui : That's gross!
Diamonit : Hum... Maybe we could use this to our advantage... Don't you have an outfit that could show more skin Rui? We must appeal to our male readers!
Rui : WHAT ARE YOU TRYING TO MAKE ME DO?! PERVERT! SHAMELESS WRITER! YOU'RE THE WORST!
Diamonit : Hey, stop it Rui! It hurts! Ouch!
Okay now, you're happy? I even got bruises now!
Anyway, see you for the next character presentation!