Sanzen Sekai no Karsu wo Koroshi (三千世界の鴉を殺し) - is a sci fi BL Drama CD-series based on a light novel series with the same name (I haven’t been able to read the light novel-series yet, but I do love the Drama CD-series! ^>^
There’s sci fi, alien, and supernatural aspects to the story. It’s full of action and intergalactic intrigue, but more than that, I love the chemistry between the voice cast:
-Suwabe Junichi in the main role (the army-hacker-psychic) Lucifardo Oscarstein,
-Miki Shinichiro in the other leading role (the army-surgeon), Saradin Aramudo…
…but also people like George Nakata (father of the main character), Kenta Miyake!! (a detective/police here but All Might in My Hero Academy), and Canna Nobotoshi (another medical doctor), but also (unbelievably!), Norio Wakamoto!!! No kidding! (he appears in a minor role)
There’s an astounding female cast as well, though, as a BL fan, I’m not equally god at pinpointing everyone’s names through their voices alone (so sorry, no cast list, but it’s a note-worthy one if I ever saw one. Sanzen Sekai has perhaps THE best female cast I’ve ever seen in a drama CD.
It’s a very professional production through and through; casting, music and sound all-together. Romance is a central thread throughout the story, but still isn’t pushed very far as it’s mostly focused on the sci fi and thus refreshingly exiting and fun through-out. (though I do adore the theme of gay romance in space! )
More info can be found on the BLCD Wiki which I highly recommend as a place to find new stuff you like, whether it’s because you like a particular voice actor or a creator of a story, it’s all searchable!
(It’s only in Japanese though, unless the title is English. I use Anime News Network as an intermediate to get the kanji for voice actors’ full names and then search the database on BLCD Wiki)