#1 MC's mom got cancer when he was 15. She fought for 5 years and finally died. During this time, MC did nothing but care for his mom. Didn't meet girls or date, didn't make many friends. His only friend is a girl who practically grew up with him, and she's in love with him... but he has (so far) not accepted her advances. Meanwhile, he learns that his Mom wrote a book for him.
#2 MC's mom got cancer when he was 15. She fought for 5 years and finally died. During this time, MC did nothing but care for his mom. Didn't meet girls or date, didn't make many friends. His only friend is a girl who practically grew up with him, and she's in love with him... but he has (so far) not accepted her advances. Meanwhile, he learns that his Mom wrote a book for him.
#3 You lose your mother to cancer after caring for her for 5 years. She left you a magical book that transports you to Serenity Island... a paradise with nekos, romance, and adventure.
#4 Serenity is a kinetic adult visual novel that has you playing the part of the MC... whose mother passed away from cancer. She left behind a book for him that when read, would transport him into the world of Serenity.