As the Mishima Zaibatsu, led by Jin Kazama, waged war on the world, G Corporation got conquered by his biological father Kazuya Mishima, and is seen to be the only force that could oppose Jin. Kazuya then puts a bounty on Jin's head for anyone who can capture him. Jin's reaction was to announce the sixth King of The Iron Fist tournament, so he could fight with Kazuya himself and get rid of G Corporation.
Meanwhile, a young Tekken Force officer led a coup d'état to slowly dismantle the Mishima Zaibatsu and G Corporation, in order to end the war. During an operation, Lars stumbles across a female sleeping cyborg, who then woke up and identified herself as being Alisa Bosconovitch. G Corporation forces attack, starting a fight which ends in an explosion. Most of the people present were killed and Lars himself barely survives with amnesia. He then goes with Alisa on a journey to discover their origins, while meeting and fighting other Tekken characters on the way.
Lars eventually meets with his comrade Tougou, and both keep in touch. Lars gradually recovers his memory back, and reminds himself of his connection to Heihachi Mishima. Lars locates and confronts Heihachi, saying that he knows Heihachi is his father. After refusing Heihachi's offer to work alongside him, Lars ponders killing him, but relents at the last minute and leaves.
After saving Julia Chang from a G Corporation facility, Lee Chaolan offers his services to aid him. Kazuya, however, takes cognition of Lars and targets him.
Lars and Alisa reach the G Corporation's H.Q., but they're received by a squadron. Tougou arrives just in time to provide back-up for Lars and Alisa, who eventually defeats both Anna Williams and Kazuya. After that, Lars reaches to a dying Tougou, and vows to avenge him, unaware of Raven, who sees him at a distance. They then hijack a Zaibatsu subway train to get to the Mishima Zaibatsu's Central Tower, although they are ambushed along the way by Nina and a squadron of Tekken Forces. Despite the odds, Lars defeats the soldiers and kicks Nina off the train.
Lars and Alisa reach the tower and confront Jin, aided by a surviving Nina. In a turn of events, Jin reboots Alisa's memory bank and sets her against Lars, while revealing that she was built as her bodyguard and as a monitor or Lars' actions. After defeating Alisa, who escapes the scene alongside Jin, Raven offers his aid and the information of Jin's whereabouts in the desert. Lars accepts.
The duo locates an abandoned temple in the middle of the desert, where is said it holds an ancient demon known as Azazel. They find Kazuya and Anna there as well. Kazuya learns that Lars is his half-brother, something that he sees as "a cruel joke". Kazuya leaves alongside Anna, but not without saying to Lars that the Mishima is cursed to nothing but constant betrayals, and that is something that he won't be able to escape from. Lars and Raven reach the heart of the temple, and locate Azazel. During the battle, Azazel says that it is a creation of men, and that is not use to keep delaying humankind's destruction. He then apparently self-destructs.
After fleeing from the collapsing temple, Lars and Raven confront Jin once again, who is accompanied by an altered Alisa. After the fight, Alisa returns to her former self and says to Lars that he was the only person who treated her as a human being, before shutting down. Jin then teases Lars, calling Alisa a worthless piece of junk, and both fight. After that, Jin reveals his true intentions: having known about Azazel for a long time since the spiritual warrior Zafina's story, Jin knew that the only way to get rid of his accursed Devil blood curse in him (which is stated that he is still in half-control of it) by awaken Azazel was to fill the world with negative emotions, and the best way was starting a war. Jin then says that Azazel isn't dead just yet, as he is to be destroyed by someone who has the blood that is cursed by the Devil Jin; just then, all who have fallen from the war could be revived.
As expected by Jin, Azazel, who grew stronger, erupts from the rubble, and tries to attack Jin. However Jin is immune to his attacks, and runs towards him only to shove his fist throught the demon's chest, sending them both plummeting to their apparent deaths. After that, Lars takes Alisa back to Lee, so he can repair the android's body. Raven appears to bid farewell, giving Lars the rebel badge after the revived Tougou gave it to him, and then leaves. Then, he receives a call, and gets a new assignment.
Lars is seen driving his SUV through the Middle East, as he witness Heihachi as the returning leader of the Mishima Zaibatsu announcing the seventh King of Iron Fist tournament. He later arrives at the Souq, just in time to save a numb Jin Kazama from the many Zaibatsu soldiers hoping to retrieve him.
He later arrives at a seemingly abandoned facility to meet Lee Chaolan and a newly-repaired Alisa Bosconovitch, who is really happy to see Lars again. As Lars was about to explain why he brought a comatose Jin with him, Nina and the Tekken force invade the facility. They stall the Tekken force away from Jin for as long as possible, but a helicopter captures him; fortunately, it is Lee who was driving it. As Lars and Alisa rendezvous with Lee atop the Violet Systems building, he explains it was all part of the plan, and since they had Jin, it has all worked out beautifully.
When the narrator of the story mode first sees Lars, he says he expected someone completely different; even older. In a conversation, Lars tells him that he's the illegitimate child of Heihachi; he was only born as a means for Heihachi to convince himself that he doesn't have the Devil Gene. The narrator also overhears Lars telling Lee that to end the war, they have to put everything on Jin. Later, he watches the Zaibatsu satellite's live broadcast of Kazuya's devil reveal, frantically ordering people to confirm the viability of the footage.
After the reporter goes to the Zaibatsu's HQ in order to hear Heihachi's story, Lars receives a message about the reporter's whereabouts in the pier; he later retrieves him back to the base. Then, Lars and his group witness the ultimate battle between Heihachi and Kazuya through images of Lee's spy satellite. After that showdown, Lars watches over a crumbling city turned warzone, as Lee and Alisa confirm the worst fears: Kazuya's G Corp has no intention of stopping the war. He then tells Jin that it's up to him to stop Kazuya once and for all, to which Jin complies.