I think the Bravos of the world can readily sympathize with Kashigi Yabushige. His liege lord, Toranaga, has been in lethal peril since he was six years old, trusts no one except himself, remains cool even when faced with seemingly inevitable failure, and has great confidence in his abilities to ride the unreliable winds of chance. He plays within the rules of the social hierarchy of his society, and utilizes them effectively, but it’s clear that they mean little to him since he doesn’t hesitate to break them when he feels it is necessary.
Yabushige follows Toranaga’s orders and executes them well, only to reliably discover afterwards that his actions were part of a different plan than the one he thought he was following.
YABUSHIGE: One of these days I'd like to know about your plan before it happens.
TORANAGA: I'll keep it in mind.
One has to feel an amount of pity for Yabushige, a long-suffering Bravo stuck with a Sigma instead of a proper Alpha. Once, just once, he’d like to know what’s going on.
On a side note, the actor Tadanobu Asano, who plays Yabushige in Shogun, is very good as the lead in the Anglo-Japanese mystery series Giri/Haji, in which he plays a completely different SSH role.
UPDATE: Loath as I am to get into questions of HOW and WHY related to the SSH, one theme that does seem to appear regularly with regards to historical Sigmas is childhood experience that leads to a lifelong reluctance to trust anyone else. Consider this incident from the biography of the real Ieyasu Tokugawa, and note that Matsudaira Hirotada was his father.
In 1548, when the Oda clan invaded Mikawa, Hirotada turned to Imagawa Yoshimoto, the head of the Imagawa clan, for help to repel the invaders. Yoshimoto agreed under the condition that Hirotada send Ieyasu to Sunpu as a hostage. Oda Nobuhide, the leader of the Oda clan, learned of this arrangement and had Ieyasu abducted from his entourage en route to Sunpu. Ieyasu was just five years old at the time. Nobuhide threatened to execute Ieyasu unless his father severed all ties with the Imagawa clan. Hirotada replied that sacrificing his own son would show his seriousness in his pact with the Imagawa clan. Despite this refusal, Nobuhide chose not to kill Ieyasu, but instead held him for the next three years at the Mansho Temple in Nagoya.
As Nemesis mentions above in reply to Menandros, I think Sigmas can and do attract loyal followers in a lesser fashion to alphas. But those followers must be under no illusions whatsoever about the Sigma's personality. It could be more akin to running in parallel for long stretches, but just a couple feet behind so that when the Sigma veers off in an unexpected direction the followers can continue as usual for a time until the Sigma pops in front again. In contrast, followers of an Alpha are usually given time to make the turn with the Alpha even though they follow more closely behind.
As an example of Sigma followers, many of us would not be following Vox in any way if he did not happen to have many general interests that aligned with ours and because he is often clearly ahead of us in real terms for those interests. But we already know there is a mid-level probability that in a few weeks, months, or years Vox may decide to sit in a dark room and not come out again, and if he does come out again with a new take in something, then okay. We were plodding along without him, it was just a lot slower going.
Interesting (possibly relevant) exchange from a "personality test" session with an industrial psychologist:
IP: A, what's your idea of appropriate disclosure?
A: I'll tell you anything you want to know.
IP: B, what's your idea of appropriate disclosure?
B: I'll tell you what I want you to know.