Too OP? Nah (Male OP reader x crossover)

Chapter 19

3rd Person POV

Both armies clashed into each other and hence the war begun, this war though.. was one sided. The sirens were easily slayed by Y/N's army, people were turning into rocks while the power houses fought the Siren power houses. Y/N was up against Tester, the sadistic one but he was toying with her. Castoria casted her abilities on everyone, they're granted with invincibility, attack up by a 100x, 

Tester: " Do you mind staying still~ And let me hit you~ I need to satisfy everyone here by killing you~" 

Y/N: " No, I don't think I will." 

Tester fired more missiles targeted at Y/N but he easily dodged all of them, to him, the missiles look like flies moving in slow motion. He proceed to sheathed out his blade from his suit and Yamato on his other hand, his suit is now glowing red. He flew in to attack her and he succeeded by cutting of her cannons, however, the parts grew back 

Tester: " There's no way you can kill me~" 

Y/N: " Where's the X button?" 

Y/N continued to land attacks on Tester, with every hit, he made sure none of the parts regenerate as he destroyed the atoms that made up Tester's suit, he then procced to set her on fire and made her suffering prolonged, upon doing this, he fired weapons from the GoB targeting her hands and legs. It pinned her into a mercury web that Mizu made. She was seen struggling trying to escape he web but her struggles were useless. 

Y/N: " Now, since you're on this web, I want to ask you something before I end your life." 

Tester: " I will not answer~" 

Y/N: " You've just made your suffering worse." 

Y/N activated his third eye and brought her into an illusion, in this illusion, she was being tied onto a chair where many Y/N was seen. She was being detached slowly part by part starting from her head, meanwhile, Y/N was searching the memory of Tester. He managed to find what he we wanted, which was where the 'Creator' was hiding, apparently, it all started with the black cube and it was hiding under the reactor of the Siren's base. Back to reality, she was screaming in pain and Observer came to her aid. Before she could land a hit on Y/N, she was shot by Kurumi as the bullet went through her head. 

With Kurumi and Observer's fight. 

 Observer: " Let's end this quick so I can kill the rest~" 

Kurumi: " My pleasure~" 

Kurumi called out Zaphkiel and shot bullets at Observer, she dodged them all and fired some of her own. It was stopped by Kurumi when she countered with her own bullets. Kurumi fired Aleph towards Observer, she dodged it and thought it missed her. However, she was proven wrong when she the bullet returned from where it fired and took down two of her cannons. She then tried to improve her situation by flying higher up in the air, Kurumi followed her and fire some bullets to slow her down. Before Observer stopped, Kurumi fired Stvarnost, re-creating the same battlefield but it's empty, deciding to test her new power, Requiem of Death, she paired this up with a new reality as now, she is the Observer of this reality, she's the puppeteer and Observer is the puppet, Requiem of Death causes the victim to suffer slow, painful death. In Observer's case, she was showered with bullets then regenerated, this will continue until the Kurumi is satisfied with it. 

Deciding that it was enough, she undid the reality and fired Blackhole toward Observer's head and when she did, Observer dived down towards Tester when she heard her scream. This was her last attempt to save her family, she activated her self-destruct system and closed her eyes.