In Another World With My Smartphone: Volume 7 by Patora Fuyuhara

16-year-old Mochizuki Touya has it all. Grand Duke of an upstart nation, inventor of goods ranging from hula hoop to caramelized popcorn, administrator of Babylon, and pilot of the Anti-Phrase Frame Gears. The western nations love him... but darker machinations unfurl in the far east. Yulong, the glorious Empire of Heaven, regards Touya with envious eyes, brazen enough to send assassins into Brunhild! To make matters worse, the mysterious young girl known as Sakura seems to have a connection with these dark assailants. In the background, dark forces gather. Something big approaches. Something far greater than anything Touya has ever faced before. Brace yourself... for a tale of swords, sorcery, and absolute calamity.