New Delhi, Aug. 1 -- Koshiyama Ryotaro, a 33-year-old in Hokkaido, northern Japan, used to pay little heed to politics. But a few years ago he discovered a reformist mayor in western Japan who live-streamed his council meetings on YouTube. Mr Koshiyama learnt video-editing and posted clips of parliamentary debates and rallies, hoping "to show people how interesting politics is".

Mr Koshiyama is part of a broader shift. Thanks to younger, social-media-savvy politicians, disengaged younger Japanese are taking more interest in politics. In last year's upper-house election-when upstart parties of various stripes made striking gains-turnout among 18- and 19-year-olds rose from 35% in 2022 to 45%; among those in their 20s and 30s, it jumped by...