Hiro has appeared in several popular Japanese magazines in which he has done phot shoots, interviews, news reports, etc. Some such magazines includes several editions of Animedia, Newtype, Ani Raji Grand Prix, Voice Animage and Seiyuu Grand Prix.
In the 8 episode OAV Angelique: Twin Collection, Hiro performed the 7th ending theme song "Kokoro ni Kakeru Niji" as his character in this series, Marcel.
On October 10, 1998, Hiro did an interview for the Japanese magazine Voice Idol vol 1. This spread was about 6 pages long and included both information from the individual interviews with Hiro and his group members, as well as a "Weiss event report" that provided an update on the projects that he and his group were working on.
In the 1 episode OAV Anime Tenchou , Hiro performed the ending theme song, "Dancin' For Your Number", along with fellow cast members Akira Ishida and Souichiro Hoshi.
Hiro has voiced several characters in Japanese video games such as Marcel in 8 parts of the Angelique game series, Carlo in Bakusou Kyoudai Let's & Go!! Eternal Wings, Wing in Magic School Lunar!, and Yoshitora Tokugawa in Samurai Spirits Zero / Samurai Shodown V.
On August 23, 1998 at the "2nd Ani Raji Festival", there was a competition for seiyuus that Hiro entered for Radio ROM Punch that would determine the new hosts of this radio show starting that September. The competition was in groups of 2, and Hiro's partner was Mika Kanai. Each group talked a while and the judges picked who they liked best. Unfortunately, Hiro and Mika did not win, but was 2nd best.
Hiro has made a guest appearance at over 47 special events such as the "2nd Ani Raji Festival" on August 23, 1998; the "Senkaiden Houshinengi event in Osaka on October 14, 2000; "the "Comic World Taipei" on February 15, 2002; the "PFM2 Mini Live and Talk Show" on June 28, 2003 and the "Neo Romance Festa Ange Party at Pacifico" on December 9, 2006.
Hiro's fellow seiyuu and "Weiss" group member, Takehito Koyasu, has stated that Hiro likes older women. One such proof of this is Hiro's fond admiration of Nana Okada, an older idol from quite a while ago.
Although Hiro doesn't play many games often, he enjoys doing brain teasers such as puzzle games and another game called IQ.
Hiro's shoe size is 24 centimeters (size 6 in mens).
Hiro is known for having a voice that sounds young for his age. This has helped him gain roles in anime for charatcers who are either young or have soft voices.
Yuuki has voiced the character Stanley "Stan" Marsh on the Japanese dub of South Park, the popular animation in America.
Yuuki is involved in a seiyuu quartet that includes hisself, Tomokazu Seki, Takehito Koyasu, and Shinichiro Miki. All four of these seiyuu play a character on the anime, Weiss Kreuz, and have therefore called their quartet "Weiss".
Some of Yuuki's favorite foods are seafoods such as crab and sushi.
Hiro stands in at 163 centimeters (5 feet, 4 inches) tall.
Yuuki has bloodtype B.
(Thoughts on coffee)
Hiro: I used to drink it about 5 times daily, but I don't drink as much now. Now it's only once a day.