Lewis Hamilton put Mercedes top of the pile as severe rain led to an almost total washout in second practice at Suzuka on Friday afternoon, with only five drivers setting timed laps and six electing not to run at all.
Conditions were so bad that the start of FP2 was delayed indefinitely - and when the lights did eventually go green after 45 minutes, few drivers rushed to venture out.
Ferrari's Kimi Raikkonen eventually broke the silence for an exploration lap, but it wasn't until Force India's Sergio Perez and Esteban Ocon headed out that the first flying laps were posted, with Ocon getting the best of that inter-team duel with a 1m 49.518s, some 19 seconds off his FP1 best.
Only three other drivers posted times - among them was Hamilton, who moved Mercedes back to the front with a lap in the 1m 48s bracket - three quarters of a second faster than Ocon.
Williams' Felipe Massa and Lance Stroll completed the top five, the latter having saved a wild moment of aquaplaning that sent him perilously close to the barriers on the outside of Turn 1.
Six drivers, meanwhile, opted to sit out the session entirely - Red Bull duo Daniel Ricciardo and Max Verstappen, Haas pair Romain Grosjean and Kevin Magnussen, Mercedes' Valtteri Bottas and Toro Rosso's Pierre Gasly.
Carlos Sainz, meanwhile, managed to go out for two quick installation laps, Toro Rosso having repaired the extensive damage incurred in his heavy crash in FP1.
The rain is expected to last into tomorrow, with the prospect of both FP3 and qualifying being held in wet or mixed conditions.