Basically Hajime's help is disabling the magic security net of magic traps, magic alarms, magic detection, etc that's in the imperial palace. He also helps Princess Liliana from being raped by her soon-to-be fiance, the Emperor's shitty son Baius who basically is a womanizer and rapist.
During the celebration party of the alliance between the empire and kingdom, the Hauria strike. Think of Hauria's infiltration like Splinter cells chuuni ninja version. Guards are being taken out strategically and killed silently. Thanks to Hajime disabling the magic security net, the Hauria are also using teleport magic items that let them teleport into imperial palace. The Hauria attack the celebration party and hold people hostage. Hajime and crew basically act as bystanders. The Emperor thinks Hajime is involved but can't prove anything. The Hauria have also set explosives in various locations during their infiltration. Hajime is listening in on the comms chatter of the Hauria doing their thing, he basically created magic communication ear pieces.
Meanwhile Liliana after being rescued is wearing a black dress, her expression made it clear she was only there for her duty as a royal. This causes a stir as Liliana and Baius look like an unhappy couple. Liliana with her stern expression and Baius who looks completely annoyed and upset. Hajime basically cause Baius's little son to not work as intended for a short time. Hajime and his girls think something happened and blame Hajime for it. Hajime confesses that he helped Liliana from being raped by Baius.
Hajime ends up dancing with Liliana and to the outsiders point of view, Liliana looks happier with Hajime than with Baius. During their dance, Liliana knows she'll be raped by Baius and abused by his mistresses. Hajime makes a random comment about how she'll be saved either way even if he didn't do anything, he particularly comments that Baius at least won't go unscathed, particularly if the empire falls tonight. Liliana is confused by this comment. After a few more words, Hajime returns to his girls, only for them to ask him why does he make girls all fall in love with him?"
Soon after the Hauria's prep is complete and they do a countdown while the celebration party is about to celebrate glory for human race. The party lights go out plunging it into darkness. As noblemen try to coordinate, they each get taken out, death by decapitation or stabbing or by arrows.
Hauria fight against the Emperor directly. The two clash with Hauria using their tactics and the Emperor using magic to fend off the Hauria. The Emperor falters due to being hit with poison arrow earlier and takes another arrow to his leg. The Hauria disable the Emperor by cutting his ligaments and he is defeated in front of the surviving noblemen. Shea also fought with her family and tribe in her own way.
Liliana panics as she immediately blames Hajime for being the cause.
Shea's dad Cam talks to the Emperor, but due to the Emperor's defiance, Hauria start executing certain hostages. Some the Emperor's close aides. It takes a few times but the Emperor shuts up as his men's lives are in danger. Cam brings up a necklace, the Necklace of Vows. A special magic artifact that Hajime created that will kill the wearer if they break their promises, not only will it kill the wearer, it will also kill anyone who shares their bloodline. Cam basically wants four pledges to be kept.
1. All beastmen slaves released.
2. Never to invade the beastmen's territory Haltina again.
3. Stop taking beastmen slaves and treat them as equals.
4. To turn the above three into Imperial edicts
The Emperor asks the obvious "if i refuses" Cam calmly states they'll kill their officers and officials one by one. Terrorize the Empire until the beastmen race is destroyed. Basically threatened even civilians, even children. Emperor refuses to yield and Baius gets dragged out for all to see and then decapitated right there. The Emperor still refuses to yield despite seeing his son murdered. Cam calmly comments that the Emperor never really loved his children, that he cared more for his friends and subordinates than his own family. Cam gives an order and a large explosion happens somewhere in the imperial city. Cam gives the order a few more time causes the Emperor to yell out "Wait!"
Emperor finally yields as he cannot win. The Hauria have bombs placed at various places and at least a good number were placed in civilian locations as the Hauria still viewed all as guilty. The Emperor finally swears and makes the vow to do all the demands and the necklace is placed on him. Cam forces the Emperor to do all of the promises within the day and almost blew up another target. The Emperor complains to Hajime about his involvement and needs healing to get all the stuff done and makes sure to yell at his subordinates to not attack Hajime as they'll die meaningless deaths.
All the beastmen slaves are freed and returned to Haltina, where a number of happy reunions happen. Some try to attack the Emperor as one of the conditions was for him to personally lead the members back but Hauria fight back protecting him and stating they personally achieved this goal, not the beastmen as a whole. Hauria state they will hold both the beastmen side and Empire side in check. Hauria also recruit other rabbitmen to join them, growing the Hauria into even more frightening faction.
Meanwhile Emperor and his Empire actually ask Liliana for an alliance due to the current circumstances. Liliana agrees as it is now more favorable for the kingdom, especially since it doesn't require a political marriage. There is a bit of a flaw in the plan as anyone could try and take out the Emperor and his whole family but due to the threat of the Hauria, no one seems to want to do it.
