The water pillar was the most standoffish of all the Hashira. With his constant stoic expression and his lack of enthusiasm to socialize, other Hashira tried to interact, but we're met with the same behavior

When you became a Hashira, this changed. He did everything with you, and often bought onigiri to eat with you. Mitsuri and Shinobu were happy he was finally hanging out with someone, while Sanemei and Obanai just rolled their eyes

One day you were talking with Giyuu (although he wasn't talking with you) and you spotted some flowers. He didn't notice, but you picked one and held it out to him with a smile. He looked a little shocked, before taking the smal blue flower with a soft smile. He looked back up at her with adoration and awe before his tiny smile dropping and returning back to normal

Giyuu: We should get back to the other Hashira