I could claim that I felt it was worth reminding everyone that Nanase can do this by showing it, but really, that's just my excuse for devoting a comic to Nanase using Fox to pat herself on the head.
Panel two Nanase sort of looks to me like she's expecting a kiss, which wasn't what I was going for. Her eyes are closed because leaving them open AND looking through Fox's eyes would make things weird for her (though it IS an option), and I tried to combine that with a surprised expression.
Looks a bit strange, but what the heck, maybe someone's face should look strange when they're effectively controlling two at once.
That said, I'm pretty sure I wrote something earlier as a follow up to what I said about ambient magic usage in the previous comic. Let's see... Whoa. That's a lot.
Clarification of previous commentary:
When a spell costs more magic than a person has, and they supplement with ambient magic, one of three things will happen:
1 - They use up most, if not all, of their magic power, and the ambient magic does the rest.
2 - They use up a little of their magic power, just enough to get the ball rolling, and ambient magic does the rest.
3 - The same as 2, BUT the amount is so small that it's almost impossible to notice, and does nothing for training.
Which happens is dependent on the person, the spell, the means of casting the spell, and how much ambient magic energy is nearby.
An average person with very little magic would almost always get results 2 or 3. At a minimum, this used to apply to Ashley.
Sarah using one of Tedd's magic watches would get result 3.
Sarah casting her one, huge spell gets result 1. It needs a bigger push from her just to get started.
Casting several small spells under your own power is better training than one big spell that uses up all your energy, regardless of whether ambient magic helps at all. However, casting one big spell that uses up all your energy is better than nothing (unless you overdo it).
Result 1 is better than nothing for training.
Result 2 is close to just casting weak spells under your own power, and is pretty decent for training if the ambient magic doesn't dry up. Weak spells cast entirely under your own power are more reliable.
Result 3 is useless for training in and of itself, but being enchanted will gradually improve magic resistance and energy. This has diminishing returns past a certain point, however, and slows down fast.
Still, Sarah was above average in some regards before getting her spell just by virtue of being enchanted so many times.