Based on the game by Bishop.

How to make an anime opening?

There are a few things you will need. A Song Is the anime about depression and dealing with loss? Choose a slow, sad song. Is it about a boy’s journey to becoming the best sumo wrestler ever? A fun catchy song is what you want. Or is it about a girl who wishes to kill everyone? Find the most hardcore song in your disposal. Visuals You can use clips from actual episodes or make something original.
You need to convey what feelings the main character has throughout the story or what the plot is.
Include the protagonist and antagonist facing off for a few seconds.
Make sure the audience understands what kind of anime they are getting themselves into. A Story Give the opening its own small story.
Maybe the protagonist suffers from a mental disorder that becomes more severe as the anime continues.
Show this in your opening without spoiling the actual show.
Maybe have the character in a field of white flowers which are caught on fire and slowly turn to ashes.
This can be a representation of the main characters sanity and the fact that they are no longer themselves by the end of it all. After compiling these things you need to edit it down to about a minute to a minute thirty, you don't want it to be too long but don't make it too short either.
After making more adjustments and adding a few more details, you should be done! If you need an example of a great opening (In my opinion) then I recommend watching “91 Days.” You don't have to watch the actual anime, just the opening, ok? Alright, hope this was semi helpful..