Sirius

In both anime: MC watches his whole family get slaughtered by vampires and his brother sacrifices himself to protect him. MC joins an anti vampire crew. MC later finds his brother alive as a vampire and loses will to kill vampires. We ship MC and brother instead of his waifu. 

- vampires against a different species - both have brothers with a difficult relationship - both protagonists have experienced cruel things 

When I start watching Sirius I said is this a 2nd version of Owari no seraph I mean is just too many common things. First The MC saw his family getting killed by vampires but he has got saved by his brother who sacrificed himself, then saved for a 2nd time by a person whom the Mc respects such as a father. So our protagonist decides with the help of [his father-like figure] to join an anti-vampire organization to revenge from the vampires. Then finds later that his brother isn't dead yet but turned into a vampire Also, both protagonists have some kind of mysterious hidden power -The animation, characters development are just very good so I highly recommend both animes. read more 

Both have similar setting with the protagonist joining an organisation/group to seek for revenge after being saved by a person who the protagonist respects (fatherly-like figure). You would honestly ship the two in the anime together (mikayuu, yukhail). Both has vampires as the antagonist as well. However, the magical element is not brought out as much in Sirius than in ONS. 

- Both involves battle between Humans and Vampires - Both includes a main protagonist that reunites with someone very close from childhood, which turns out to be teamed up against you. - Sword Fighting - Emotional Backstory with character development - Main protagonists both have a secret/hidden power 

Sirius is so much alike with Seraph of the End in terms of the anime genre and theme, the main characters being close to each other in terms of relationship and name and the goal of the MC in both anime is essentially the same if not similar. It's a great anime to watch before or after watching Owari no Seraph so try it out. 

Both are vampire stories taking place in the early 1900s in an European- influenced Japan. Both have good visuals as well. 

Both series have similar vibes, are set in the 20s, and revolve around hunting down vampires. 

In both anime, the action takes very quickly and dynamically. Main caharacter is similar to Koku, and main vilians is identical to taht criminal organization. 

These series are based in the genres of action,thriller and with a touch of romance, with both having a protagonist with a unique personality that escapes from being generic. And the cherry on top of the cake is without question the great animations both of the animes have. Definitely worth watching. 

Just a similar vibe. They both are about killing demons. Demon slayer has more found family elements.  

It also has vampires and it has a kind of, similar setting. But Hellsing Ultimate is more mature in my opinion. 

Set in similar looking time period, bot are action fantasy with some supernatural elements. One has fairies, the other has vampires and angry puppies.  

Both are set in pre-ww2 imperial Japan (Kamuy in 1911 or so and Sirius in 1930), and both feature japanese soldiers. Both at one point feature Japanese-occupied Sachalin and nature scenery. Both feature a zeppelin-type aircraft. There are groups looking for a treasure in both, but many more sides of conflict in Kamuy. The protagonist's side in Sirius is playful and kind but professional and efficient, while in Kamuy the team constantly picks up and drops out very independent, strong characters of whom you never know if their interest align. Kamuy definitely has stronger characters and is more original in both story and designs/direction, and Sirius I find more polished and beautiful when it comes to backgrounds, effects and the artistic side. read more