After discovering the "peppery citrus" note of the sansho peppercorn in his uncle's forest, the gin fan bought a distilling unit when he returned to the United Kingdom and experimented with other botanicals from Nagano.
He says: "We pick perfectly ripe berries, fast-freeze them for freshness and express-ship them to the UK for distillation with juniper, coriander, angelica, sweet orange, almond, liquorice and lemon peel."
Kokoro Gin's first batch of 1,000 bottles sold out within a couple of months and distribution to Singapore started earlier this year, followed by Indonesia and Hong Kong. The Japanese-inspired gin will head to Japan later this year.
Another Japanese gin pioneer is artisanal gin distillery The Kyoto Distillery, which launched Ki No Bi, which means "the beauty of the seasons", in October last year. Its founding partner is Englishman David Croll.
Like the name suggests, the best ingredients representative of each season are chosen as botanicals for the rice spirit-based gin.
These include yuzu from Kyoto, hinoki or Japanese cypress wood chips, red shiso leaves, bamboo, Uji green tea and green sansho Japanese peppercorns. Water from Kyoto's sake-producing region, Fushimi, is used to reduce the gin.
Ki No Bi is currently exported to a few overseas markets, including Singapore and Hong Kong. Mr Croll says: "We'll be launching in the States later this year and expect that to be a major market for us."
Close on the heels of these two craft gins is the launch of Okayama Craft Gin by Miyashita Sake Brewery, a distillery based in Okayama, western Japan, that is more than 100 years old.
Using 10 botanicals, including Japanese peach, grapes and coriander and a rice shochu alcohol base for a softer and sweeter finish, the gin is then aged in oak barrels until it acquires an amber colour and smoky fragrance.
The demand for craft gin did not go unnoticed by heavyweight breweries Suntory and Nikka, which have won worldwide acclaim for their whiskies and are also facing a shortage in aged whisky stocks.
Unlike whisky, which takes years to age, gin can be bottled after a few days of resting from distillation.
Nikka launched the Nikka Coffey Gin in June and Suntory released its Roku gin early last month, targeting the high-end gin market and retailing for above 3,000 yen (S$38) for a 700ml bottle.
Ms Emiko Kaji, international business development manager for Nikka Whisky, says: "The firm estimates the premium gin category grew by 50 per cent this year compared with a year ago and it expects higher growth in this category this year ."
Nikka's Coffey Gin uses the Coffey still, also used for whisky distillation, that was imported from Scotland in 1963.
Suntory's Roku is so named for using six (or roku in Japanese) botanicals - sakura flowers, sakura leaves, sencha green tea, gyokuro green tea, sansho peppercorn and yuzu - on top of the classic gin botanicals, including juniper and liquorice.
Suntory public relations executive Tomoko Fujiwara says: "Gin's flavour varies according to its distillation process and botanicals. I see many possibilities for the Japanese market, which is still relatively new and open to gin."
Speciality craft gin bars have also been popping up on the scene.
The Good Meals Shop, which opened in Shibuya in 2014 offering 30 types of gin, now serves more than 230 types of craft gin, including Japanese craft gin.
Mr Takeaki Miura, owner of the bar, says Japan's distilleries, which have traditionally been used to make shochu, tend to make a smoother, rather than dry, type of gin.
He adds: "The industry is still in an experimental phase in terms of the use of botanicals and spices. I think it'll take another two or three years for the market to hit the right notes."
His bar is in the final stages of distilling an original craft gin, after three years of trial and error, to be served later this year.
"Japan has soft water and a rich variety of botanicals, plus superb craftsmanship, so Japanese gin is going to get a lot more exciting in the coming years," he says.
Kyoto Distillery's Mr Croll says gin in Japan has traditionally been served as a base cocktail ingredient. However, Ki No Bi is being consumed like whisky - straight, on the rocks or with a dash of water or tonic.
"As Japanese bartenders now start to learn more about the emergence of local and craft gins, consumers are sure to pick up on this new category. The domestic market potential is very high," he adds.
•Tor Ching Li is a freelance writer.