Just found out about black lagoon and I heavily enjoyed it.
Finished all three seasons and caught up in the manga. It's rock solid, **ha**, fight scenes are fun, character are great **except the sauske daughter wannabe hacker** -- especially Rock: who goes from scared office worker to cold calculating person that even freaks Revy out (I watched the english dub which made him abit edgy since he was vioiced by Light's english voice actor and they kept using the term game), and it's story **prev arc is kinda boring though**>>10708
I've only seen the first episode of Demon Slayer, all I can really say is that it seems fairly cool and the main character is nice.
If you're unsure just use the three episode rule, if the show doesn't interest you in three episode then drop it