Yuki, ranked 71 places below his compatriot at 174, beat top seed Somdev 6-2 6-4 in one hour and 41 minutes in the semifinals of the USD 50,000 hard court event.
Later, Yuki also made the doubles final with New Zealand partner Michael Venus as they trounced Ruben Gonzales and Artem Sitak 6-2 6-1 in just 52 minutes.
In his singles match, Seventh seed Yuki did not face a breakpoint in the first set and capitalised on two of the five he earned on Somdev's serve to nose ahead.
Yuki will now fight it out with unseeded Russian Alexander Kudryavtsev, who shocked second seed and compatriot Evgeny Donskoy 7-6 (4) 6-3 in the other semifinal.
It will be Yuki's third Challenger level final in his career. Last year, he won the Traralgon event in Australia and ended runner-up in Kaohsiung in Taiwan.
In the doubles, the second seeded Indo-Kiwi pair will face India's N Sriram Balaji and Blaz Rola, who defeated Ti Chen and Marek Semjan 6-3 7-6 (5) in one hour and 15 minutes.