Detective Naomasa Tsukauchi is an earnest, hardworking individual who has earned the right to be a close friend of All Might. As a detective working with the law, Naomasa is strict and does not approve of vigilantism, which despite having heroic intentions, is still illegal and therefore makes them "Villains". He is shown to take his job and the law seriously. He is also hesitant with requesting All Might for help, believing that to be taking advantage of his personal contacts and be potentially compromising in the future. Naomasa also cares a lot for his sister, Makoto. Makoto would often tease her brother and challenges authority (although not to the point of committing anything illegal), which would annoy Naomasa quite a bit. However, the two can get to the point of argument. Despite being rigid with the law and doing things by the book, Naomasa is eventually willing to trust vigilantes, and even Villains, if he knows they genuinely want to help, or can provide useful aid. 

If you could sound similar to his English VA, Alejandro Saab, that would be great, but it is not required!

There's not any good clips for him online, so looking at some scenes of him throughout the anime would be ideal! He first shows up in episode 13 of season 1, so look for him there!