Lucius Modestus, a Roman architect specializing in *thermae* design during Emperor Hadrian's reign, developed an early passion for bathhouses inspired by childhood visits to his grandfather's public baths. During one such visit, he slipped underwater and experienced a brief, disorienting transport to a modern Japanese bathhouse—his first encounter with time travel. As an adult, professional setbacks with rejected designs and waning inspiration plagued Lucius. Seeking solace in a bathhouse, he discovered a drain that again propelled him to modern Japan. This phenomenon recurred whenever submerged in water during career dilemmas. In Japan, he observed innovations: fruit-flavored milk, sophisticated indoor plumbing, hot stone spas, onsen etiquette, and themed bath designs. Though misinterpreting the Japanese as "flat-faced slaves," he deeply admired their bathing technology. Lucius adapted these concepts for Rome. Early projects included renovating his grandfather's bathhouse with Japanese elements. His reputation soared after designing an outdoor bath overlooking Mount Vesuvius for Consul Lepidus, incorporating observed natural heating techniques and monkey-inspired features. He later created space-efficient indoor baths for his friend, marble sculptor Marcus Pietras, a frequent collaborator. Commissioned by Emperor Hadrian for a private villa bath, Lucius encountered modern Japanese toilets and bidets. This inspired his "aquarium" design featuring sea life mosaics and advanced water systems. This success led to military assignments, where he developed healing hot stone spas for soldiers, improving circulation and pain relief based on Japanese spa observations. His relentless work strained his marriage, particularly when accepting commissions for Hadrian's adopted heir, Lucius Aurelius Caesar. Professional challenges included designing baths for diverse audiences: creating etiquette signage for foreign soldiers using Japanese pictorial rules and balancing luxury with modesty in public baths inspired by Kinkaku-ji temple aesthetics. During these projects, he met a fellow architect in Japan, leading to an exchange of design insights that respected cultural traditions. Lucius evolved from a struggling architect to Hadrian's lead bathhouse designer. His later works focused on ambitious large-scale public baths honoring imperial figures. Throughout his career, the recurring time-travel encounters provided continuous inspiration, shaping his philosophy that bathhouses should foster relaxation and social harmony across cultures.