The Pirates have a solid foundation for a good, long-term bullpen with David Bednar, Colin Holderman, Carmen Mlodzinki, Dauri Moreta, and Ryan Bocuki. But the Pirates could certainly get more depth, especially another left-hander and one with experience closing games out. One option to pursue could be Yuki Matsui.
Matsui just turned 28 at the time of writing this. The southpaw pitched to a 1.57 ERA, 0.89 WHIP, and 5.54 K:BB ratio with the Rakuten Golden Eagles. Matsui has a 32.4% strikeout rate, as well as a 5.9% walk rate. He is also immune to the home run, as he has a 0.47 HR/9 rate. Of his six NBP seasons, he has an HR/9 of 0.5 or lower six times. The lefty transitioned to the bullpen after his age-18 campaign and hasn't looked back since. Matsui has saved a total of 236 games.
You'd think that someone like Matsui, a dominant closing pitcher, is an intimidating presence on the mound with hard stuff to back it up. But Matsui is just a 5'8", 170 pounds hurler who averages out around 92-95 MPH. He has a looping curveball as well as a splitter, but don't sleep on his four-seamer just because it's not a 97+ flamer. He's been a very effective pitcher at getting strikeouts with his finesse.
It's hard to make a good comp for Matsui. There's no good comparison as another high-leverage lefty out of the international market to compare him to. He's younger but pitches much differently than most high-leverage guys. But if I had to make an estimation, he signs something in the 3-4 year range worth $6-$8 million a season. On average, that's about how much a decent left-handed relief pitching makes a year, including Matt Moore, Brooks Raley, and Andrew Chafin made in 2023. However, since the market is thin with left-handed relief pitching, who have a recent track record of saving games, I could see Matsui approaching $10 million a year.