Koutarou Amon vs Yuji Kiba: who would win?

Yuji Kiba favored — Slight edge (~55%)

Koutarou Amon · Tokyo Ghoul · EoS

Tier
7-C, up to HIGH 7-C
Attack Potency
Large Town Level, up to Town Level+
Speed
Massively Hypersonic+, up to Sub-Relativistic
Durability
Large Town Level, up to Town Level+

Yuji Kiba · Kamen Rider · Horse Orphnoch

Tier
7-C
Attack Potency
Town Level+
Speed
Relativistic+
Durability
Town Level+

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