[4] After their mother dies of an illness, high schooler You Kogasaka and his younger half-sister Chinami move back to their childhood hometown of Hibarigasaki to live with their aunt, Shino.

While no blood is drawn or injury occurs, You forgets the name of his childhood friend, and Mare informs him that she has "reaped" his nightmare.

Its members include Asuho Minahoshi, the daughter of a local cafe owner, Kosame Hisakaki, the younger twin sister of student council member Komomo Hisakaki, and club president Haruto Okaizumi, along with third-year student Suwa Setsuna, who rarely comes to club meetings.

Hoshizora no Memoria features seven alternate endings depending on the player's choices throughout the game, all of which begin after Kosame's attack.

Asuho, who also knew You in his childhood, has kept with her a Tanabata card written by You on which he wished to reunite with Yume, the lookout girl.

In Komomo's route, it is revealed that Kosame is in fact not properly human, but is an illusory dream of similar nature to Mare.

Kosame died in an accident at the lookout during her childhood (explaining why the lookout is fenced off), prompting a grief-stricken Komomo to use her powers as a shrine maiden to give her new form as an illusory dream, using the shrine's sacred object, a meteorite, as her host object.

However, Kosame, still unable to accept that she is anything but a ghost destined to disappear at any time, ultimately asks Mare to eliminate her.

You, seeing through Mare's deception, borrows her scythe and cuts his wrists, causing him to enter an oneiroid state that allows him to perceive of Kosame, who tearfully recognizes You's love for her and decides to stay.

In Isuzu's route, You learns that she was in fact raised in Australia, but moved to Hibarigasaki with her parents due to her younger sister Suzuha's fragile health.

Isuzu, devastated after moving away from her childhood home, began to visit the Hibarigasaki science center to see planetarium shows of the southern night sky.

After the science center closed down, its director gifted Isuzu with an old telescope, along with a key to Hibari High's rooftop, so she could continue stargazing.

However, Chinami and You later give the repaired telescope back to Isuzu, revealing that they worked together to fix it in order to mend their friendship.

You's friends then work together to find the lookout girl; their search ends when Setsuna reveals that there is a patient the Hisakakis' father's hospital by the name of Yume Ototsu.

The two later sneak out with aid from Asuho, Kosame, and Komomo, visiting the lookout together, where Yume is able to get You to express his true feelings of grief from over the years.

Years later, Mare is reborn as Mea, the daughter of You and Yume, and the family visit the lookout together under Hibarigasaki's starry sky.

Throughout the game, the player encounters CG artwork at certain points in the story, which take the place of the background art and character sprites.

Throughout gameplay, the player is given multiple options to choose from, and text progression pauses at these points until a choice is made.

After living in the city for years, he and his sister Chinami move back to their smaller hometown of Hibarigasaki.

The vice-president of the astronomy club who always seems to clash with the student council at Hibari High (Hibari-Kou).

Shy and somewhat cold, she dislikes the Kogasakas at first (even sending them death threats), however she slowly opens up and becomes friends with You and Chinami.

A shrine maiden and cousin of the Hisakakis, she works for the main branch of the Seitengu and was dispatched to Hibarigasaki in order to send off a spirit.

when something upsets him, such as when Komomo threatens to abolish the Astro Circle or when she flings away flyers during recruitment sessions.

Originally the one and only member, he and You try and recruit Chinami into their respective clubs, she ends up joining the Occult Circle.

Her parents were forced to return to Japan because her body couldn't handle Australia's harsh desert climate.