Complex sentence: They are formed in 8-or 10-car sets, and the 10-car sets can be coupled to E3 series "Komachi" sets using couplers hidden behind sliding nose doors.
Split into simpler sentences: They are formed in 8-and 10-car sets. The 10-car sets can be coupled to E3 series "Komachi" sets using couplers hidden behind retracting nose doors.