Masaya Matsukaze has an impressive resume. He's voiced Teru in Death Note, Morty in Pokémon and Blues in Mega Man NT Warrior. But that's not his most famous role.
Matsukaze voiced Ryo Hazuki in the original Japanese versiosn of Shenmue and Shenmue II. Wouldn't it be great if you could meet him? You probably can!
The cafe's interior is apparently modeled after a voice recording studio and serves drinks like fruit juice and herb tea that are good for your throat as well as sweets and alcohol.
The concept behind the cafe is that it's a place where fans can interact with voice actors. In the past decade or so, Akihabara has deconstructed the barrier between fans and their heros. For example, music group AKB48 was created with the concept of "idols you can meet daily".
Voice actors are popular in Japan. It is a niche market, and not mainstream celebrity in any way. There are, however, voice actor magazines and websites covering the industry. Some voice actors release music CDs, while some even have their own trading cards and fan service goods, like hug pillows.
One of the neat features at Seiyu Café is "Seiyu Jukebox". For a fee, you can have a seiyu recite lines from previous roles. The fee varies from voice actor to voice actor.
The cafe's official site doesn't have a list of voice acting talent staffing Seiyu Café, but apparently there's a more detailed list at the cafe.
Since Matsukaze owns the cafe, he should be around. Feel free to ask him if he knows of a place where sailors hang out. For a price, of course.