I Became Too Good at Teaching the Enemy's Professor

“Finally, retirement!” Ruin, a Demonkin who worked his entire life looking only towards retirement. And just when he thought he could finally retire. “Your house has become a Hero Academy.” “……What?” “Meaning, your entire fortune is buried there.” “……….” His life's savings were buried in the enemy nation's academy, apparently. “Damn it, I’m going to get my money.” Swallowing his curses, he infiltrated the academy. To retrieve his entire fortune. But then. “Become my son-in-law.” “Become the Imperial family’s consort, no, the hidden power.” “Speaking as a Hero. Become my commander.” He did too well at his job as an undercover professor. “……I’m going crazy!” …Instead of retiri...