The third thing a Friend must learn is about their 'presence' and 'force of will'. For reference, these words are "sonzai-kan" and "eikyou-ryoku" in Japanese. Sonzai-kan, which I translate as "presence", is a fairly straightforward translation and the characters can literally mean "feeling [of their] existence". Just note that they mean it in the sense of "a 500-pound gorilla in the room is a presence you cannot ignore." "Eikyou-ryoku," meanwhile, is suggested as "influence" in the kanji dictionary, but that doesn't really fit how they are using it here, so I'm using an interpretation of the word (which literally is "influence-power") that more matches what they mean by it.

Friends can exert a presence and force of will equal to their original forms.

If one comes from a large beast, then they can use a powerful, intimidating presence.

The magnitude of one's force of will determines such things as how much power one's blows will have.

By contrast, if one comes from a small beast, one can suppress their presence in order to hide.

If one has a small force of will, then they can move about more nimbly.

If you can master this, then it shall become a great weapon for you.