"So is this the first time coming to the beach, Kyo-kun?"
"No, Shishou took me to the beach once when I was younger. Didn't like it."
"Because of the cat's dislike of water?"
He didn't feel like swimming, but the sun was nice. Kyo stretched as he enjoyed the rays on his skin.
"You put sunscreen on, didn't you, Kyo?"
"Yeah."
"Do you mind getting my back?"
"Yeah, sure…" Kyo picked up the bottle then looked at Kazuma. "Shishou, what the hell are you wearing?"
"It's good Japanese tradition for men to swim in fundoshi."
"Yeah. Water. That's the reason."
Notes: The framing story (in italics) takes place during the beach house arc in the manga (volumes 10 & 11).
The rest (a flashback) takes place when Kyo was 11 or 12.
This came from thinking aloud about Kazuma. Through the whole series, he is only ever shown wearing kimono or a karate gi. I speculated that he never wears western-style clothing. Then I thought, "What would he wear to the beach?" The answer was obviously fundoshi.
If any one thing could mortify Kyo, it would be his dad wearing an itty-bitty loincloth in public.