Forced to Become a Son-in-Law After Transmigrating to Another World

(Shipgirls, a live-in son-in-law, a chat group, joining an organization that protects China) A special forces soldier is discharged due to injury. After a game enables two-way transmigration, he discovers he isn't the protagonist? In a chat group, everyone has a System. His System can summon famous weapons from history as female weapon spirits, including warships. But why is its gacha even more of a rip-off than Penguin's? Later, he is forced to become a live-in son-in-law, only to discover that a battle between the two worlds is inevitable. He joins China's Great Wall organization and learns that his best friend is actually his superior's superior. As countless Gates of Evil descend, how will he and China's Great Wall fight back?