Tenchu was one of the most notable stealth-focused games on the PS1, alongside Metal Gear Solid. In fact, they both released in 1998 in Japan.
The duo's stealth mechanics are where most of the similarities between the two end, though, as Tenchu incorporated ninjutsu, Japanese fantasy, and martial arts elements throughout the series. Metal Gear Solid is, well, Metal Gear.
FromSoftware President Hidetaka Miyazaki actually stated that Sekiro could have been a new entry in the Tenchu franchise, but plans changed. That confession alone should give fans hope for a Tenchu comeback.