In the drama, Inagaki Goro plays a school counsellor, 天間了 (Tenma Ryou). In the school he works at, various students and teachers come to him to seek advice, though they're not always willing to speak the truth despite wanting help. While trying to find the truth, Ryou tries to save his patients.
Senga will be playing a student, 北原蓮 (Kitahara Ren), 18, who got his girlfriend pregnant. Together with his girlfriend, they visit Ryou's room for counselling.
Other cast members revealed are Takada Sho, Nozawa Yuuki, Sanada Yuuma, and Tanaka Juri. (Just in case you're curious, Takada Sho plays a student who questions his own orientation. Nozawa plays Ryo's ex-patient who is working to save money and aiming for a CD debut. Sanada is a student with IQ 160 and gets in the way of Ryou's work. Juri led a happy life, but everything changed after his brother got into an accident.)
The drama is episodic (probably), so Senga will not appear in every episode. There is no confirmed date for when Senga will appear yet, but Takada Sho will be the patient for the first episode.
Shinryouchuu -in the Room- starts on January 12th, 24:50 - 25:20.
Source: various TV magazines Twitters, Za Teleivion ZOOM!