For all the fans or newcomers of the Tenchu series, welcome.

The Tenchu series never had a true home, first appearing on the Playstation 1 (or PSX) in Tenchu: Stealth Assassins and was quite an interesting new title, including stealth actions and new techniques for the console and future games, resulting in a prequel to the first. The two starring characters being :

Rikimaru, a silver haired, ninjato wielding member of the Azuma clan and has a scar from his past over his right eye. Rikimaru is more of the main protagonist of the series.

Ayame is also another playable character, fast and quick other than slower and more strength than Rikimaru, yet is a bit weaker. She wields a pair of kodachi (however it changes in later games) and plays another big role in the series but usually isn't considered the main protagonist of the series.

After Stealth Assassins made a bit of success, another game came out for the Playstation 1 as well, acting as a prequel and telling the story of Rikimaru and Ayame, along with a few new characters, keeping the same stealth gameplay and a few new mechanics.

The next in the main series and broke away from its Playstation home, yet still being on the next console Playstation 2, but also being on Xbox and was later released for a mobile version, and a more rare PSP Version. More of the same, but a bit of stiffness completely removed and stilll keeping the better stealth and ninja style of gameplay intact.
Of course more games were released but basically ran away from its first home, with Tenchu Z and Shadow Assassins being on Xbox 360 and the Wii, but making an appearance on the PSP with Shadow Assassins, but some didn't do as well as the previous, and wasn't as great as its previous games.

Personally to me, it all started from the very first, I specifically remembering opening it up on Christmas morning the year it came out. Nothing like it ever came out, and it was the stealth aspects that just hooked me in from start to finish. Still to this day I "ooe and awe" from the animations and kills from it.
Favorite one has to be Wrath of the Heaven. Was the perfect stealth and just...awesome game of the Tenchu series. Unfortunately, the later game just went downhill even more and they basically just gave up on the franchise.