A Japanese underground idol has stirred an online debate by offering fans the unusual perk of sniffing her armpits.

Hari Matsumoto, from Wakayama, Honshu island, has attracted over 400,000 followers on social media thanks to her bubbly personality and approachable charm.

In Japan, underground idols usually perform in intimate venues such as small theatre, livehouses or shopping centres and rarely appear on mainstream media.

Unlike top-tier idols featured on television, in magazines, and in...