A Budding Blue Sky(2012)

Drama is based on series of mystery novels by Sakaki Tsukasa - "Hikikomori Tantei". Torii is a hikikomori who can make deductions even when he's given very small amount of information. His friend Sakaki works in insurance company and he's the only person who can help Torii to break out of his hikikomori style. They begin to solve mystery cases together.