Tsunoda booked a karaoke room and invited Gasly and other team members to join him for the evening, with the results appearing on social media.
The get-together also served as a sort of an informal early farewell party with Gasly's move to Alpine for 2022 expected to be confirmed soon.
"That was definitely the highlight of my week so far!," the Frenchman said when asked about the session by Autosport. "All my karaoke experiences, I've been in Japan. Based on that, I will call myself a pretty bad singer, a pretty poor singer.
"But no, we just went there for fun. And I was like, you're jumping in. We are going to Japan.
"So Yuki, you're going to take me to a karaoke place and being there with some members of the team and I had a very romantic song together with Yuki where he got very emotional and gave all his life!
"He gave so much energy that he had to leave the room because he started to have a headache, apparently, based on what he said."
Gasly stressed that off-track moments with the people he works with are an important part of the job of a racing driver.
"That's the sort of moment which you enjoy being part of the team where it feels like, you know, a family because we travel the world altogether. Most of the time obviously it's for work.
"But then after you get these this day off and at the end of the day, we're all humans, you know, we need to share these sort of experiences.
"And these are the moments that I will remember more than, you know, a Thursday at the track, doing whatever, you know. But it's always very unique moments that you share. And I must say it that it was a really enjoyable time with the guys."
Regarding Tsunoda's singing abilities, he said: "Especially in Japanese, I must say, I had no I actually no idea whether he was swearing at us or properly singing, but it sounded pretty good."
Gasly said he was impressed by Tsunoda's high profile at Suzuka, with his image appearing everywhere.
"Obviously he is still quite new, but being racing at home is very, very unique feeling and you know, we exchanged actually on that and I told him you can be quite quickly overwhelmed with all the support that you get, all the energy. It's quite energy-draining.
"At the same time, it motivates you, but you've got to give the fans some time and some attention and you need to find the right balance to keep all your focus on the race. I mean, every single people that will come here will want him to perform on Sunday.
"But I think it's really cool. You know, he became a sort of an example to all these young Japanese, give them hopes that, you know, in three or four years you can make it to F1. And yeah, I think I find this really cool. So I'm happy for him."
