Fate: Emiya the Host Novel

Shirou discovers a Hosting System that completes tasks for him while he remains a passive observer. When he attempts to use it to clear a non-existent Holy Grail War, the system repeatedly denies his requests to learn magecraft. Frustrated, he settles for a simple goal: earn money. However, the system's methods prove problematic. It nearly forces him to rob a convenience store, prompting him to add a legal constraint. Even with this safeguard, the system's "optimal" solution is absurd—calling his guardian Taiga to propose marriage for financial sponsorship, as she happens to be the daughter of Fuyuki's largest underworld family. Shirou frantically cancels the hosting before disaster strikes, horrified by the system's logic. The system assures him there's a 99.9% success rate, but Shirou dreads what the remaining 0.1% failure might entail. Stuck with a system that technically obeys the law while pursuing the most questionable path to his goals, Shirou faces an uncertain future of increasingly bizarre hosting attempts.