The daughter of Primo Uno and Messines settled midfield before striding to third spot with a lap to run, three lengths behind early pacesetter Echelon ($3.60), who used his box one draw to advantage.
Still three lengths off Echelon down the back straight, Shimaguni made her move running into the final corner, eventually proving too strong for her rivals in the home straight, recording a three-length win over Echelon in 42.57.
The fast finishing Lady Arko ($4.60) was a further two and three quarter-lengths back in third.
Owned by the SCG Syndicate, Shimaguni improved her record to 13 wins and two seconds from just 19 starts, earning over $87,000 in prizemoney.
The black chaser will now aim to represent Victoria in the Group 1 National Distance Championship, held at Albion Park on August 25.