i leave you with these letters

(lowercase intended)
luke's gone, and has been for over a year, but when michael, ashton, and calum find a notebook full of letters -journal entries, apologies, and multiple suicide notes that weren't used- that luke had left for them, what secrets will they uncover about their friend?
possible triggers-
suicide mentions, a suicide scene, self-harm (mentions and the action of it), brief mentions on eating disorders.