I personally haven't used a Togiharu Inox knife, so what I have here is mostly a bit of conjecture, based on what I can find online.
Togiharu knives mostly seem to be available from Korin. There doesn't seem to be a huge amount of public feedback from forums or from other online reviews.
"Inox" is, as you said, a term for "stainless" and is in fact a fairly generically tossed-about word. Personally, I consider "Inox" to be the type of trigger word where I have to start digging to get any actual information. However, Korin does list the Togiharu Inox as being AUS-8, so that's a starting point.
According to BDL, another AUS-8 series of knives is the Fujiwara FKM line. Those knives are well known and extensively reviewed and discussed. The general viewpoint is that the steel in the Fujiwara FKM knives is not as hard as VG-10 knives, but is tougher and less likely to chip than VG-10. Quite a few chefs like the FKM series knives for their toughness.
You mentioned the triple combination set from Korin of the (210 mm) Gyuto, (270 mm) Sujihiki and (150 mm) Petty set. If for price alone, I would suggest you might want to glance at the comparable Fujiwara FKM knives at Chef Knives To Go. The Korin price for the Togiharu set is $345, while the cumulative CKTG prices for the comparable individual Fujiwara FKM knives is $210.
With the Fujiwara FKM's you also have the option of changing any of the choices at CKTG (after all,with the Fujiwara FKM knives you are looking at buying open stock anyway). Instead of getting just a 210 mm gyuto, you could buy a 240 mm or 270 mm gyuto. Especially with a gyuto, you should consider a 240 mm or 270 mm blade length.
Dillbert is right about concern for "situations". More expensive knives do have a sad propensity to "walk away".
AUS-8 is not a particularly reactive steel. You should not have too much problem with something like onions.
Sharpening will pretty much be the same as with any Japanese quality stainless steel knife. Read the posts and threads on ChefTalk. Specifically, invest in a 12 inch Idahone honing rod ($30). The Beston 500-Bester 1200-Suehiro Rika 5000 set from CKTG ($140) is well known and a good starting point.
Hope that helps