Honkai Star Rail: Luna Kindred's Joyful Journey

Hua Ling is the adorable Theresa, a fair-skinned, beautiful girl with big eyes. One day, he attends a comic convention with his rich, handsome best friend. He cosplays Theresa, and his best friend cosplays Otto. After many amusing and enjoyable incidents, they are hit by a speeding car driven by a frantic Durandal, transporting them to the world of Honkai Star Rail. There, a mischievous Aeon, the 'Immortal Dragon', transforms them into Theresa and a system. Hua Ling, expressing his wish, becomes Theresa, while his best friend, wanting a system, is transformed by the mischievous Aeon into a system installed within Hua Ling. They go from being 'brothers' and best friends to 'sisters' and best ji-you (close female friends), and then are picked up by the Astral Express...