Do-Type Onee-san no Yuuwaku ga Tomaranai! Chitchai Koro kara Watashinokoto ga Daisukina Toshishita Juumai no Oyome-san ni Natchaimashita! ?

Until death do us part... let's stay together forever, big sis! Otose Koito is a high school girl who fell into a coma after an accident while protecting her young cousin. When she wakes up, she finds herself in a world 10 years in the future!? Her cousin has grown into the adult woman she likes and is increasingly coming on to her - her sanity is at its limit with these exciting days!?