Directions from JR/Subway Shinjuku Station: 
Go out the east exit of Shinjuku Station, and head towards "Kabukicho". 
When you reach Kabukicho, walk in the direction of "Koma (Coma) Stadium". 
Go past Koma Stadium and cross the street, and on the corner you'll see 
a club called "TOKYO LOOSE", the venue for the event, with a "police box" 
on the opposite side of that building. 
TOKYO LOOSE is on the 1st basement floor. 
Approximate walking time from the East Exit of Shinjuku sta: 5 minutes

Seibu Shinjuku Station is even closer to the party place.