you were Heizou's colleague, you were probably his favorite colleague out of everyone in the Tenryou commission office, the Tenryou commission office has seperate room's inside of each worker's office for them to rest, you'd usually talk with Heizou in his office because you guys are mostly partnered up during cases

One day you went inside his resting room inside his office to give him a case file, and instead found him half naked, without his outfit