Seike Taroumaru vs Nanomech: who would win?

Seike Taroumaru favored — Slight edge (~55%)

Seike Taroumaru · Toaru Majutsu no Index · Base

Tier
9-C
Attack Potency
Street Level
Speed
Peak Human, up to Supersonic
Durability
Street Level

Nanomech · Ben 10 · Base

Tier
9-C
Attack Potency
Street Level
Speed
Average Human
Durability
Below Average Human Level

A heuristic estimate from normalized VS Battles Wiki stats: tier, attack potency, speed and durability.