https://skatingjapan.or.jp/image_data/fck/file/2019/190619_FS_Senkokijun.pdf
(my rough summary)
2019-2020 selection criteria for international competitions
Worlds (Men/Ladies; 3 spots, Paires/Ice dance; 1 spot)
(1) Singles (Men/Ladies)
1. Nationals winner
2. The 2nd skater will be selected from skaters who meet either of the criteria below.
a) Nationals 2nd & 3rd
b) GPF top 2 finishers among Japanese skaters
c) Top 3 among Japanese skaters on ISU's WS when Nats finished
3. The 3rd skater will be selected from skaters who meet either of the criteria below.
a) Skaters who meet 2.a)-c) but not selected
b) Top 3 among Japanese skaters on ISU's season's WR when Nats finished
c) Top 3 among Japanese skaters on ISU's SB when Nats finished
*Skaters are required to participate in Nats which is the final selection meeting for Worlds. (This requirement does not apply to substitutes.) That said, if the skater placed the 3rd or higher at Worlds in the past, and if the reason is unavoidable such as injuries, there will be a case that the skater can be selected in a comprehensive way by taking it into considerations that the skater's results prior to the injury, for example, are good enough to meet the criteria above. The perspectives of how the skater's condition at Worlds can be taken into the considerations.
(2) Pairs/Ice dance
Skaters will be selected from teams who meet either of the criteria below.
a) Nationals winner
b) Top 3 among Japanese teams on ISU's WS when Nats finished
c) Top 3 among Japanese skaters on ISU's season's WR when Nats finished
d) Top 3 among Japanese skaters on ISU's SB when Nats finished
*Skaters are required to participate in Nats which is the final selection meeting for Worlds.
4CC (Men/Ladies/Pairs/Ice dance; 3 spots)
(1) Singles (Men/Ladies)
When Nats finished, skaters will be selected from skaters who meet either of the criteria below.
a) Nats top 10 finishers
b) Top 6 among Japanese teams on ISU's WS when Nats finished
c) Top 6 among Japanese skaters on ISU's season's WR when Nats finished
d) Top 6 among Japanese skaters on ISU's SB when Nats finished
*Skaters are required to participate in Nats which is the final selection meeting for 4CC. (This requirement does not apply to substitutes.) That said, if the skater placed the 3rd or higher at Worlds in the past, and if the reason is unavoidable such as injuries, there will be a case that the skater can be selected in a comprehensive way by taking it into considerations that the skater's results prior to the injury, for example, are good enough to meet the criteria above. The perspectives of how the skater's condition at Worlds can be taken into the considerations.
(2) Pairs/Ice dance
Judging based on the international competitive ability, skaters will be selected from teams who have the minimum scores that the fed's figure skating committee requires. (Skaters need to receive the scores in competitions that the figure skating committee specifies.)
*Skaters are required to participate in Nats which is the final selection meeting for 4CC.
Junior Worlds (Men/Ladies; 2 spots, Pairs/Ice dance; 1 spot)
*The final decision is to be done in selection meeting at Nationals.
(1) Singles (Men/Ladies)
1. Jr Nationals winner
2. The second skater will be selected from Jr age eligible skaters who meet either of the criteria below as well as who is willing to participate in Jr Worlds.
a) 2nd & 3rd at Jr Nats
b) Skaters who skated at Jr GPF
c) Top 3 eligible skaters who skated at Nats
d) Top 3 among Japanese eligible skaters on ISU's season's WR when Nats fininshed
e) Top 3 among Japanese eligible skaters on ISU's SB when Nats finished
*Skaters are required to participate in Nats which is the final selection meeting for Jr Worlds. (This requirement does not apply to substitutes.) That said, if the skater placed the 3rd or higher at Jr Worlds in the past, and if the reason is unavoidable such as injuries, there will be a case that the skater can be selected in a comprehensive way by taking it into considerations that the skater's results prior to the injury, for example, are good enough to meet the criteria above. The perspectives of how the skater's condition at Jr Worlds can be taken into the considerations.
*To be in the pool for Jr Worlds, skaters are required to have done the required jump elements for Jr SP and have proven that the skaters have enough ability to skate in Jr field at any of Jr competition in the current season.
(2) Pairs/Ice dance
Judging based on the international competitive ability, skaters will be selected from teams who have the minimum scores that the fed's figure skating committee requires. (Skaters need to receive the scores in competitions that the figure skating committee specifies.)
*Skaters are required to participate in Jr Nats which is the final selection meeting for Jr Worlds.
JGP
Men/Ladies/Pairs/Ice dance
Skaters will be selected based on the abilities to do required elements, performances, and international competitive abilities in the selection meeting to be held in June.
(So complicated and long! There are some more criteria but I'm done here. Any corrections are welcome.)