歩き endurance. road-side ice hardly exists in japan. most stuff is up valleys and on the sides of mountains with 10hr approaches not uncommon.
寒いcold. -25c nights and -15c days are not uncommon. no big deal if youre climbing for a day but a serious factor when youre out for several as the long approaches demand. your gear, attitude and nutrition will have a direct bearing oon how you cope with thte cold.
遠い remote. despite a big population into the outdoors, most people visit ski areas in winter, making even the premier ice areas unvisited to the point of increasing risk. the complex nature of japans topography its normal to have whole mountain sides to yourself. in the valleys of Japanese mountains, no one can hear you scream…
危ないdanger. half a meter of snow over a day isn’t uncommon, making for deep drifts, choked gullies, cornices and avalanches. the risks are real and tho the peaks are only 3000m and you can see the lights of the train line at times, sometimes people don’t come home.
知らないunknown. this is not the alps, scotland or cascades. theres no big industry behind winter climbing to hold your hand. even if you read Japanese, beta is kept to a minimum, making the whole process still a bit of a frontier.