On an overcast day in Tokyo this week, three dozen men and women strolled through a botanical garden in groups of four, making awkward conversation as they searched for clues to a mystery-solving game — and a potential partner for life.

They are participants in one of the many matchmaking events the Tokyo Metropolitan Government has been hosting for years in an attempt, so far unsuccessful, to reverse declines in marriages and births.

Having organized parties and offered dating and fashion advice, the metropolis of 14 million now hopes for a broader reach and better results by releasing an artificial intelligence-powered dating app as early as this spring.