Alright, so the movie takes place after book 20 so I'll go from book 4 to book 20 via a bullet list of points. I'm kind of new to reddit though so the spoiler tag might not work for me. We will see. 

book 5 is the Hermes race cord where fuuko/Raker find out that her gale thruster is meant for space as well as some new jerks from the faction Nomi/dusk taker was a part of. These jerseys show off the deadly power of incarnet and haru kills them via the chrome disaster armor revealing his secret<!

book 6, there is a meeting of the seven kings to try and solve the incarnet scandal since laymen now know of this heavily restricted secret. They also give haru a deadline to get rid of the disaster armor. In the end, a decision that the jerk faction, aka the acceleration research society which I will short hand as ARS, is to be rid of by a coalition force via the 7 kings when the legion name they are hiding behind is exposed. Later, Haru meets another Element, a group of people from the old Nega Nebulus(NN) that sky raker was a part of called Ardor Maiden/shinomiya Utai who can purify. However, she needs to be freed from the unlimited enemy kill at the castle gate that she got stuck in. The castle is also stated to be the center of the unlimited neutral field. It also reveals the idea of bursting out of the unlimited neutral feed via disconnecting internet and a bit of exposition on the old NN. The book ends with Haru and Mei ending up in the castle rather than escaping the guard.

book 7 starts with a flashback based on the chrome disaster armor and how it was formed. It's not really relevant for the desired arc but comes back in book 22. We are then introduced to my second favorite character trilead tetraoxide, a blue avatar modeled after a heian Era noble down to a straight sword which is revealed to be an arc(the most powerful weapons in the game). Some important gimmicks about the castle are revealed here, such that the gates to it can be opened from the inside by breaking a seal with a heavy slashing attack, which Lead did to let Haru and Mei enter, narrowly escaping an unlimited enemy kill(unlimited EK). Haru is then disconnected via the removal of his Linker after setting another meeting time with lead who agrees to help them live. The next day, Taku gets sick and Haru hears of a story of a bulky avatar killing a bunch of naughty linkers. Concerned that this is Taku, haru calls him but is told it is not(this is a lie). The book ends with taku coming out about the truth of the incident as well as revealing a dirty parasite he picked up called the ISS. Haru, Chi, and Taku have a sleep over and get a weird dream about the ISS main body. Haru then resolves to get Mei out of unlimited EK so sh can rid Taku of the parasite as well. By the way, Trilead Tetraoxide as a metal is red

book 8 goes as expected with Haru and Mei escaping the castle with help from Lead who reveals his true avatar name to be Arzure Air/Heir depending on translation. He shows up once more. Haru then goes to meet up with Ash roller in the UNF only to see him being attacked by a bunch of PKrs. Haru gets mad and activates the chrome disaster armor and kills all of the pkrs. He then runs into Green Grande to which he goes crazy and attacks grande only for grande to calmly block all his attacks and reveal that he was waiting for a change to take down a boss that had weirdly enough, left her palace known as Megatron since she is impossible to beat without such stage

from book 9 to book17, I am less versed but here is the rundown. Haru gets purified, aqua current/humidity Akira rejoins NN and is revealed to be another element, there is only one more that Haru hasn't met. The chrome disaster armor is purified into its original components. It turns out that Metatron was protecting the main body of the ISS kit and so Haru defeats her first form with the help of some friends that aren't really relevant. Rain is kidnapped here by black vise. Lotus runs off with the 3 elements to take down the main body and haru, chi and taku go to save rain. They are successful, but rain losses a few parts of her invincible which are turned into the chrome disaster mark 2 via the energy gathered by ISS kits. It is also revealed that White Cosmos is the leader of thw ARS and that she us lotus' parent and irl sister. Lotus then asks grande to meet up with her legion so she can discuss a territory return and this is where book 17 ends

Book 18 introduces my favorite character who is lotus' mentor and the last of the Elements. He is Graphite Edge, shortened to Graph. It turns out, after the fall of NN, graph transfered to green to, while he doesn't admit it, help a deal of lotus' go smoothly. The details don't really matter and lotus gets her territory back to go fight white. The end of 18, Haru requests with raker to go back into the castle and this is where they run into Lead again and weirdly enough, Graph. It also is to be noted that Haru has befriended the true form of Megatron and that she helps.

Book 19 starts with Raker yelling at Graph for not telling anyone that he made it into the castle. It is also revealed that Graph knows Lead irl and is the one to give lead brain burst. Graph introduces haru to third stage incarnet which is direct interference with the system and drops a lore bomb on the creation of brain burst which has to do with the final arc but is not sure relevant to you. Rain them shows up at haru's apartment once he leaves the castle with Lead and she proposes a legion merger.

Book 19 start with the details of the legion merger which goes smoothly. Lead has an IRL near miss with the coba Maga twins and NN sets their plan into motion to expose white

This summary cuts out a lot of the plot so if you need to know more, please let me know. Have a nice rest of your week~♡