I kind of agonized for a while for the best way to translate these terms... Other runners-up for the "force of will" are "force of personality" and "aura".
I dunno if they should teach Goji-chan this one, since she was originally... what? 118m tall?
"Presence" is a weird thing in anime. It really isn't physical, but it's treated almost as if it is, but only to creatures that perceive it. Hence, you can have, say, a Yakuza mob boss that can literally knock people off their feet with a sour face and have them whimpering that they can't even move their limbs because the pressure is so intense, but it's still just in their heads, and won't even rustle a piece of paper. (In the far extremes, a tennis serve is suddenly the meteor that killed the dinosaurs... but again, only in their heads.)
Hence, Goji-chan will get more scary (you can see them flinch and the background go grey when Goji gets it right, even before she demonstrates), but the "presence" part, which just makes her feel like a giant monster, has no effect beyond intimidation. (The "force of will" part actually imparts more force, but that's still within her own bodyframe's dimensions.)
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.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.
