Not so much to do with anything within the game, but it has been mentioned that this is the first Visual Novel to end up on the front page of Game Faqs, placing 1st on the most wanted Faqs on the site before someone submitted a complete Faq.
At its peak, it made the 3rd top rated PC game and 11th top rated game.
By the end of Lilly's route, Hisao himself has managed to survive and recover from not one, but two major heart attacks. The man is nothing short of determined, to say the least.
Also, many dudes wouldn't resist the temptation of going further with a girl who is either drunk (Hanako) or high on too-strong medicines (Rin) and thus is openly throwing herself at them. Hisao is Wise Beyond His Years and, both times, he manages to keep his desires aside.
In Hanako's route, Hanako manages to successfully open up. Even in her bad ending, as painful as it may be, she has the courage to tell Hisao that his coddling makes her unhappy.
One specific moment is the pool bar outing the two share where Hanako shows a more relaxed side to herself.
Also in Hanako's route, Mutou knows exactly what to do when Hanako has her panic attack. And so does Shizune.
Hanako also has one in Lily's route, via first deciding to join Naomi and Natsumi's school newspaper, and then planning to travel to Kyoto. On her own.
Also, in Emi's route, who comes to the rescue when Hisao and Emi almost break up. It's someone whom you wouldn't expect... Misha! Quite the surprise, and if you take her advice, she'll be the key to get Emi's Good Ending.
Shizune also deserves some credit, since she told Misha to intervene. If you make the other decision at Emi's house, Rin gets her own when she essentially forces Hisao and Emi to face the issue by leaving the rooftop.
Hisao gets a great one during Act 2 of Emi's route, when he receives Iwanako's letter. In it she basically apologizes for distancing herself from Hisao while he was in the hospital... but Hisao just crumples the letter and throws it away, declaring that he doesn't care about that, since to him the hospital was a long time ago and he feels that his life is now in Yamaku with his new friends. Seeing him having grown so much and becoming so determined to not feel sorry for himself is a HUGE moment of character development. You can't help but cheer for the guy.
Not really, if you see Iwanako's letter as a corollary of a Break the Cutie process for her instead. It's nice to see Hisao look forward to the future, but not necessarily when he unintentionally ended up hurting a girl as painfully shy and fragile as she was during these days. Also, Hisao's act is meant to mirror Emi's tendency of running away from the more painful elements of her past by pretending they aren't there and always blazing full-speed ahead. Hisao later realizes this is not healthy behavior, which leads to the action below...
Because the REAL CMOA comes when he takes her letter out of the trash, reads it in full, and puts his bitterness behind him.
The tour Hisao gives Misha of the school late in Shizune's route, recalling all the experiences he's had with her and Shizune, and urging her not to push Shizune away like he did with his old friends. It showcases his Character Development and is a crucial step in repairing Misha and Shizune's friendship