I still don't get it, if this is a database to be used by your game then why are you asking us how you could make it better? We don't know what information you need.
First of all, I'll again suggest you use
the wiki as it is likely to have better information.
Second, put everything into one sheet. If you are trying to make a legit database then your very first concern should be how can I best organize my data, and having your data in tons of sheets doesn't accomplish that. If you want things to be readable or convenient then you use some kind of program that will interpret the table for you. This is why we have SQL.
Are you doing all of this by hand or are you using tools to mine the data out of the wiki, and manipulate the database.
Moving on to actual data issues:
Any particular reason you have underscores in all the names?
Abilities sheet: A48, why is Prismriver Sisters a character, and why does it and the 3 sisters all list the abilities of all the sisters?
Abilities sheet: A98, Same thing but with the fairies of light.
Age: Age is a number, and if I'm using a database to find a number I expect to get a number back. What I don't expect is a history lesson. I would strip everything down on this page and turn it all into "Unknown", "[age]", or ">[year]". Also don't forget units. If you want some of this other stuff you've written here then I suggest an additional column called "Age Notes" and fill that in when clarifications and evidence, but keep the Age column clean and concise.
I already broke down B77 as an example of how you seem to be giving superfluous information. "Unknown, but one of the oldest gods; she far predates the invasion by the Goddess Kanako and the Yamato in the Great Suwa War approximately 2300 years ago". Now we'll read this knowing that we are interested in the age. "Unknown", good start. "but one of the oldest gods", vague, but clearly we know something so her age isn't really "unknown". "she far predates the invasion by the Goddess Kanako and the Yamato", how does this event compare with being one of the oldest gods? If having lived through this invasion makes her one of the oldest gods then there is no point in including the bit about being one of the oldest gods. "in the Great Suwa War", Oh this invasion has a name? Why even bother mentioning Kanako and the Yamato? "approximately 2300 years ago", if you have this number then why didn't you just say so? What was the point of the history lesson just now? The point is that you should try to be concise. I would remove everything about Suwako's age and just put ">2300". Someone using a database to look for her age will not care about what happened 2300 years ago which makes us think she was alive back then.
Occupation: A48, A98, once again, you've got the triplets all saying each others occupations.
Description: Alright, there's a lot of work that can be done here and hopefully I can explain to you why this page kinda defeats the point of a spread sheet. You've got 2 sets of data, Names and Description. By putting them into this table you want to relate members of the Name set with members of the Description set. That is, I want Hakurei Reimu of the Name set to be associated with that large member of the Description set. Here is where I see a problem within your table. When I look at the member of Description that corresponds with Reimu, I see 2 more lists, a list of games and a list of descriptions. Now, not only do I have to associate Reimu with a Description but I have to also associate games with Descriptions and likely also Reimu with games. The concise way of representing this data would be to make a column for every game, and then write descriptions where applicable. Reimu has lots of descriptions so she fills almost everything... until I want Reimu's description for Great Fairy Wars, which returns, to me, an empty cell because no such description exists.
Relationships: Now if we apply the logic from the previous sheet to this sheet we find that the most concise way to make this sheet is to make one column and row for every character in write relationships where applicable... This is gonna be a massive sheet and its why I brought up that stuff earlier about things not being meant to be readable.
Appearances: Ugh this data doesn't really lend itself well to being in a spread sheet. Like, you could make a column for every game but then you've still got stages, and then you've got some special notes. I'll say you can just leave this one like it is.
Titles: Again, column for each game, fill data where applicable.