Mecha: A Different Three Kingdoms

My name is Liu Bei. I woke up one morning to find that my two roommates and I had transmigrated into the Three Kingdoms era. No weapons, no horses—just the three of us squatting by the roadside chewing on hard flatbread when Cao's army surrounded the town. Zhang Fei was the first to blow. He lunged forward and transformed into a black off-road mecha on landing, his twin axes cleaving half the street apart. Guan Yu moved next—a red heavy-duty motorcycle burst out of the flames, and with one strike he split the enemy vanguard, man and horse, clean in two. They turned back and shouted for me, Liu Bei. I clenched my fists, but nothing stirred on my body. Still, I had to survive this battle first. Then I'd go drag back the three men this chaotic era hadn't found yet—Zhao Yun, Ma Chao, and Huang Zhong—one by one. — Description from novelcodex.org