Since the film has just aired in Japan, spoilers coming to those who watched the film started surfacing online and it seems that earlier spoilers found online coming from those who watched the pre-screening are true! To kick things off, we will start with the first segment in this film, Skull's Message for W.
Kamen Rider W: Skull's Message for W
Note: Events that happened in the 90's are italicized.
The film starts with W fighting the Ptera Yummy and then Ryu shows up not transformed and tries to help fight, swinging that sword around. When Shotaro asks why he didn't transform, Ryu tells him to not ask questions. Then Akiko shows up and says in English this, "Kamen Rider no more" and hits him with the slipper... with its own veil!
The Yummy activates the Memory Memory after he finds out she has a connection the Kamen Riders and it takes her back to past to the year 1999 and see his father's past.
Sokichi was trying to make coffee, but he burned it. He and his partner, Matsu talk a little bit, and then they go to a girl named Melissa and we are shown in a scene in which she sings in a club. At the show, the Spider Dopant shows up and attacks, and Sokichi tries to fight it, but he gets caught. He uses the Stag Phone to get himself released after he gets stuck in the spider's web. The Dopant escapes.
Meanwhile back at the underground of the agency, Shroud is assembling the SkullGarry/RevolGarry. This is when we learned that the two are childhood friends. We learned that Shroud has a background knowledge regarding Dopants and she warns Sokichi about it earlier. After Sokichi tels Shroud that he has seen the monster that she was talking about, she then gives the Skull Memory.
Also, Shotaro and Marina were at the show and Shotaro is amazed on how badass Sokichi was! Sokichi wants to know more about attacker, so his partner, Matsu begins his search in a library. Take note that the music from when Philip goes to the Gaia Library is playing while he is making the search! Sokichi then shows up and it shows that his partner had made a display like they used during the second part of the arc back in the TV series to show all the connections and basically sum up what had happened during the previous episode.
Akiko wakes up from the Memory's effect and then W HeatMetal was getting ready to do a Maximum Drive to destroy the Yummy, but then Akiko pushed him out of the way because she wanted to see more of the memories. The Yummy tried to escape, but she grabbed onto it while it was flying, and the Memory's effect still activated.
The Bat Dopant shows up in here somewhere and then Sokichi goes to the club owners house to find Melissa, but instead he finds the Bat Dopant again with the Spider Dopant. They fight and Sokichi becomes Kamen Rider Skull Crystal for the first time, thanks to Shroud throwing the belt at him and it transforming automatically. It was described that his first transformation is similar to BLACK's.
During the fight, Skull gets pinned down by a vehicle by the Bat Dopant (who has the ability to make vehicles move by using sonar on them) and during the time he's pinned down, he gets a call from a young Akiko, angry that daddy never attended to her birthday party! In which we have this really funny exchange:
Akiko: You didn't even come back for my birthday!
Sokichi: I'm very busy, I'm almost crushed to death!
Akiko: Let's see if you dare pull such a stunt when I get married!
Sokichi: I'll definitely turn up for your wedding. *hangs up*
That gave him the strength to get out from under the vehicle. Future Akiko seeing the scene said, "Even at that time, when I was on the phone with him, he was a Kamen Rider."
She was upset because all her friends, her boyfriend, and even her father were Kamen Riders because when she needs her boyfriend or her father, they need to go and fight. Their priority is fighting, so that's why she didn't want Ryu to be a Rider anymore.
We are then demonstrated with the Spider Dopant's ability to "tiny spiders make loved ones blow up" thing by having the club owner get blown up when his wife touches him. This was proof that the owner wasn't the Spider Dopant like Sokichi originally thought.
It turns out, Matsu is the Spider Dopant! The reason why he becomes the Spider Dopant because he loves Melissa and becomes jealous of their relationship, thus he become the first person to buy a Gaia Memory.
Sokichi was enraged because of what he Matsu did with those people and pursues the Spider Dopant but before that, Melissa makes Sokichi promise that he won't kill him. He promises and then goes off. Skull then gets attacked by the Bat Dopant who was controlling an oil tanker. Skull fights her on top of the tanker and then summons the SkullGarry to help. The Bat Dopant is defeated and she reverted back to Eren Komori, the user of the Memory. She begs for Skull's mercy but Skull is resolute.
He then goes after his partner and fights him. In the end, he uses his Maximum Drive which killed Matsu. We are shown in a scene in which Melissa mourns over Matsu's dead body and calls Skull a monster. Even at the end, Sokichi still considers Matsu as his "partner."
Then we are shown back to Future Akiko saying that Kamen Riders are a kind of curse and then it goes back to the future, where the Ptera Yummy is holding the Memory Memory and it starts swirling with power and shoots a beam of light into the sky. End Skull/W portion.
Some minor notes about this segment: Accel Trial, W FangJoker, W LunaTrigger never appeared also, a certain Stone died in the segment which is described by our source is like the 90's version of Watcherman.
The second and third part of the spoilers will be posted later once the one who placed the sequential spoilers online will post it. To those who have read his original post, I added some details posted coming from other spoilers found online.
Special thanks to Winter Chevalier of HJU for sharing your experience with us and to DecaEnd of HJU and Deadpool of HJU for the bits of spoilers!