Description
Natsu Iwashimizu is a 16-year-old girl from Saitama, born on April 7. Severe bullying led her to become a hikikomori, withdrawing completely into her room and harboring bitterness toward society. While her family, especially her mother, showed kindness, her grandmother subjected her to verbal and physical abuse, calling her useless or dumb. Her sole emotional connection was with her pet cat, Macadamia Nuts, named as a pun on her own name meaning "summer".

Awakened centuries later in a post-apocalyptic Japan as part of Team Summer B, she initially exhibited extreme shyness, social awkwardness, and an apologetic demeanor, frequently bowing and accepting blame even for incidents beyond her control. Thoughts like "There's no one on Earth who would be interested in me" reflected her lack of self-worth, driving her to prove her usefulness by meticulously noting and cataloging edible plants and resources for the group, fearing she was a burden.

Her early interactions featured dependency on Arashi Aota, the first person to show her kindness, leading to unrequited romantic feelings. She often acted considerately toward him to gain approval, a behavior noted and criticized by Semimaru Asai. Semimaru's teasing and bullying—pulling her hair, playing pranks—initially worsened her insecurity, though his actions later revealed a complex dynamic intended to toughen her up.

Character development unfolded gradually. Key moments included her intense guilt after Arashi was poisoned by mushrooms she gathered, reinforcing her "It's All My Fault" mindset, and her jealousy upon discovering a letter from Arashi's girlfriend, Hana. She initially hid the letter but, after introspection and Semimaru's intervention, acknowledged her selfishness and returned it, prioritizing Arashi's happiness.

Her resilience grew through mentorship. Semimaru taught her self-reliance and emotional honesty. Ango, a member of Team Summer A, initially saw her as a replacement for his deceased friend Shigeru but later valued her conscientiousness and hard work. She practiced skills like the "Whip-off-the-tablecloth trick" under his guidance and eventually stood up to his overprotectiveness, insisting on taking calculated risks.

Pivotal growth occurred when she rescued Semimaru from danger, openly weeping in relief, and later independently devised a plan to save Ango and Arashi from a perilous situation—her first major act without relying on others. This marked a shift toward self-confidence and assertiveness, culminating in decisions based on her own judgment rather than seeking approval.

Her practical contributions remained vital, including naming newly discovered species and navigating challenges like menstruation in the harsh environment, which attracted iron-eating bacteria due to her blood. Despite lingering insecurities, she evolved into a tenacious and careful survivor, recognized for her observational skills and quiet determination.