Oleander

Nerium oleander, a captivating flower which can be seen in the colours pink, red or white. They can grow up to two to six metres tall and are incredibly fatal when consumed.
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Riku Nadami is struggling. He has undiagnosed and untreated severe depression, his parents forced him to move to an entire new country where it's a 50 50 chance of the temperature being either too hot, too cold or a secret third option, his new school is the absolute worst and the students keep staring at him.

His life continues to get worse when he finds a mysterious flower growing out of the cracks of his wooden floors.