See-through
Chapter 0: pain of hiding unrequited love for popular friend until discovered that it was mutual. Chapters 1-4: long time school friends continue to be friends until college, the other one(who comforts) hold feelings for the other while the other one have long time unrequited feelings towards a girl and keeps on getting rejected, the comforter friend have a hallucinated/ideal version of his unrequited love and have relationship with him but later realized that it was result of his feelings and made the hallucinated version disappear. Chapter 5: an accidental vouyer met a senpai who did it with someone at some abandoned place, the senpai discovered and interacted with him but eventually discovered that the partner have a gf already was using the senpai but it was two way usage, after the vouyer comforted and confessed, the senpai told him to wait until taller than him but he disappeared until returned one day as teacher.
Yoake E No Senkou