Previously it was planned to include the Blu-ray Collection's Kamen Rider Saber Spin-Off from Blu-ray Collection BOX 2, but it seems like it will be included directly from BOX 1 releasing on May 12th. The Spin-off is titled as "Sword of Logos Saga".
This will once again depict the Incident from 15 years back and it will reveal that Hayato Fukamiya (Kamen Rider Calibur) & Daichi Kamijo (Kamen Rider Saber) going their separate ways from Sword of Logos being linked to the same ability of Ankoku-Ken Kurayami's ability to reveal the events of Future to the user of the sword.
It was the time when Tetsuo Daishinji was officially recognized as Kamen Rider Slash, as the Swordsman of Sword of Logos. Hayato Fukamiya (Kamen Rider Calibur) was struggling with the 'Vision of Future' shown to him by his Seiken - Ankoku-Ken Kurayami.
Hayato Fukamiya: "Will this World end up in Destruction?"
Looking at the sad expression of Hayato, Daichi Kamijo (Kamen Rider Saber) who is his best friend tries to encourage him. But the Seiken shows him even more cruel future against Hayato.
Hayato had to make a decision and with this in his mind he decides to meet Master Logos in Southern Base.
Hiroyuki Hirayama - Daichi Kamijo / Kamen Rider Saber / Kamen Rider Calibur
Mitsuru Karahashi - Hayato Fukamiya / Kamen Rider Calibur
Keisuke Soma - Master Logos
Masashi Mikami - Kenshin Nagamine / Kamen Rider Blades
Yuki Ikushima - Ryo Ogami / Kamen Rider Buster
Hiroaki Oka - Tetsuo Daishinji / Kamen Rider Slash
Rina Chinen - Sophia
Along with the known Previous Swordsman, we'll also get to see the Previous Kamen Rider Espada & Kamen Rider Kenzan.
Mei Angela - Reika Shindai / Kamen Rider Sabela
Takaya Yamaguchi - Rintaro Shindo / Kamen Rider Blades
Ryo Aoki - Kento Fukamiya / Kamen Rider Espada
Eiji Togashi - Ren Akamichi / Kamen Rider Kenzan
Since the story will focus on 15 year old events, it's not known how will Reika and the three Swordsman will appear in the Spin-Off.
The Screenplay is by Hiroaki Uchida who had recently worked on GARO -VERSUS ROAD-, Ultraman X Episode 12 & Ultraman Orb Episode 20. Spin-Off is directed by Koichi Sakamoto.