what's greek for tsundere?

[misheard]

Title: what's greek for tsundere?
Fandom: Fate/Grand Order
Character(s): Ritsuka, Castor
Pairing(s): Ritsuka/Castor
Genre: Fluff
Word Count: 400
Rating: G
Warnings: None
Summary: When trying to get Castor's attention, it's best to be as absolutely unsubtle as possible.
Notes:

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A multilayered problem: Castor is much easier to get along with when he's not around Pollux, but when he's not around Pollux his main focus becomes reuniting with Pollux. Castor has his own interests like anyone else, but he considers them less important than Pollux.

Which is why, when it comes to getting Castor's attention away from finding Pollux and keeping it there, it's best to be as absolutely unsubtle as possible.

"Castor, I like you."

"Hm?" Castor only glances at Ritsuka. "Of course you do. It's an honor to have the favor of Divine Spirits like Pollux and I."

Even less subtle, Ritsuka reminds himself. "No, I mean I have a crush on you. Not your sister. Just you."

"…Eh?" Now Castor fully turns toward him. "Don't try to flatter me. I'm not kind to humans, and I won't fawn over you like your other Servants do."

"That's why I like you. Because when you do say something nice to me, I know I've earned it." There are plenty of Servants who fell for him just because he was their Master, not because of anything about him as a person. Castor he knows for sure will never give him special privileges because of that.

"…You're surprisingly masochistic, human." Castor scoffs, but there's color in his cheeks that wasn't there a moment before. "Very well. Help me find Pollux and I'll reward you for your devotion."

As soon as Castor is reunited with Pollux, he'll probably forget all about this conversation, but even the chance of a reward from him is too tempting to pass up. "Got it! I'll find her right away."

Ritsuka has a few good guesses where Pollux might be, and it isn't long before they spot her about to enter the combat simulator. Ritsuka gives her an apologetic look as Castor accosts her with there you are, he was so worried, why didn't you invite him to train with you, what other sparring partner could you need, etc.

He's about to leave them alone when Castor says, "Wait." Stiffly, he pats Ritsuka on the head. "Thank you for your help."

"Brother?? What happened while I was gone?" Pollux asks, as Ritsuka looks giddy and touches the top of his head where Castor's hand just was.

"Nothing! It's not important."

"I feel like it was something important!"

"Do you want your head patted too, sister?"

"No! …yes."