[Matrixbeast]

Power Rangers happened. That's how I was introduced.
There was a TV special that was basically Jason and Zach's actors talking about Zyuranger, and I remember a clip of Bandora singing. That spurred interest in Sentai, but this being before the internet was widely available, I couldn't act much on it.

In the early 2000's, I came across a VHS of Kamen Rider Couga, about 3 unsubbed episodes of Kuuga (Note: It wasn't a bootleg.) My family frequented a Japanese video rental store (Grandmother is Japanese), so after getting sick of browsing anime that I probably shouldn't have been watching, anyway (They had tons of the edgy 90's OVAs), I stumbled upon this not-Power Rangers looking guy and rented it. Didn't understand a damn thing.
While this was technically my first foray into Kamen Rider, I was only about 13 and didn't know what was going on, so I don't really count it...
They also allegedly had B-Fighter Kabuto. I recognized that as Big Bad Beetleborgs, however it was always unavailable so I never got a chance to rent it (I think someone just bought it and the store just never bothered removing it).

Meanwhile, Lost and Found in Translation happened in Dino Thunder. This spurred interest in my brother and I for Sentai, and eventually (Read, years later) we ended up finding Magiranger subbed. I hated it but still, technically my first. I would later try to watch Shinkenger subbed (Alongside KR Decade, which I watched in full) due to Shinkenger's crossover.

So, yeah. Power Rangers, Japanese video store, and an episode of Dino Thunder X-teen years later.