By thinking of Brain & April 1st, it might only remind you of that 2 year old April Fool's Joke called "Kamen Rider Brain" which will premiere in the year 2035. It says it's the spin-off of something. Kamen Rider Brain was supposed to be the Spin-off of Kamen Rider Drive and part of Drive Saga.
Today on April Fools day they have revealed about the Drive Saga: Kamen Rider Brain with " #AprilFools?" in it. It is strange for them to use "?" (question mark) after hash tagging April Fools. And will they use the same joke twice?
The RIDER TIME event where it was hinted was on March 30th. Will they start April Fools prank two days before it, especially at an official event?
Another thing is, Kamen Rider Zi-O has already reached Episode 30 and Episode 31 & 32 to be Agito Part, but we still don't have Kamen Rider Drive. Geiz might have already gained Drive Ride Watch but that doesn't mean that not even a side character will appear. Ryoma Takeuchi might be pretty costly for producers to bring into TV Series just like Sota Fukushi, but there are chances of bringing Brain's actor Shota Matsushima instead.
According to the April Fools Joke from 2017, it had mentioned that Kamen Rider Brain will premiere on 2035, it could make Kamen Rider Brain the Mirider from the year 2035.
When a Kamen Rider Staff had hash tagged Kamen Rider Brain's teaser as April Fools Joke, Shota Matsushima had replied "Don't make it a joke!!!!!!!!".
In another tweet he had mentioned "If this is a lie then I will leave the Handkerchief in front of Oomori Producer's House and leave".
Even I am not sure whether this is true or an April Fools Joke. Toei's April Fools Joke is pretty confusing. They have revealed the pic of Kamen Rider Ginga in a way for people to believe that it is a Joke.
If RIDER TIME → Drive Saga: Kamen Rider Brain is true then it will start streaming somewhere in April at TTFC and it will also be Heisei Rider 20th Anniversary Official Work. If this is true then Kamen Rider Brain will be Heisei's Last Rider. Yes, Heisei hasn't ended yet. Reiwa will begin from May. Today was only the announcement of the Name of the New Era.