I think they're a girl but I'm not sure. This page has Tousaki with both a male hint (Adam's apple) and a female hint (pointed chin), Tomoaki with an Adam's apple and a square chin, Ibuki with no Adam's apple and a pointed chin, and Tsugumi with an Adam's apple and square chin). If you estimate shoulder width by the backpack strap it looks like both Tousaki and Ibuki have narrower shoulders than Tomoaki and Tsubumi but that could just be a slim guy. The earrings and hair dyeing hint female but as a musician who knows, and Tsubumi has earrings but he's a "cool guy".
This is what I have in my notes:
Howa, Tousaki (F?)
o) Short blonde hair with dark bangs covering left eye
o) Class 2-E
o) Light Music Club
o) In class hike group
o) Loses pick during hike