It is 8:30 on a cold Saturday night in mid-December. Around the East Exit of Shinjuku Station, immaculately dressed and preened people of all ages are waiting, smartphones in hand, for their friends or co-workers to arrive.

Many of them are likely about to embark on a night of eating, drinking and revelry in one or more of the hundreds of restaurants, bars, karaoke boxes and clubs packed into the sprawl of crowded alleys that make up one of Tokyo's top entertainment districts.

Among the throng is a small group of six volunteers from three continents — two Japanese, two Europeans, an American and a Costa Rican — who are here for a very different night out. They are tonight's Tokyo Spring Homeless Patrol, and their mission is to deliver vital goods to the homeless, those ghosts of Shinjuku who sit freezing and hungry in their cardboard-box homes, seen but unseen by the red-faced crowds walking to the next warm bar or on their way back to their well-heated homes.