It is also a personal league best for the England captain the Bundesliga’s most expensive transfer at 100 million euros who scored between Musiala’s two goals but was taken off injured after sliding into the post late in the game.
The win lifts Bayern to 60 points in second place, with Leverkusen, on 67, travelling to Freiburg on Sunday.
The visitors had the upper hand from the start but it was Darmstadt who struck first, with Tim Skarke slotting in to polish off a quick break that caught Bayern off guard in the 28th minute.
They did not have to wait long for an equaliser after teenager Aleksandar Pavlovic, fresh from being picked for the Germany squad for friendly matches later in March, dribbled past three players, charged into the box and found Kane, who passed to Musiala to finish the move in the 36th.
Kane then completed their comeback in stoppage time with a diving header but Bayern almost conceded another themselves when Darmstadt’s Oscar Vilhelmsson hit the crossbar on the stroke of halftime.
Germany international Musiala, in superb form, put the game to bed in the 64th minute with a stunning solo run for his 10th league goal but they were not yet done.
Substitute Serge Gnabry and Mathys Tel both got onto the scoresheet before Vilhelmsson bagged another goal for Darmstadt, who also hit the woodwork once more late in the game.
