ʜᴀʀᴜᴋᴀ - ꜱᴄʜᴏᴏʟ ɢɪʀʟ ʏᴏᴜ ᴏɴᴄᴇ ʜᴇʟᴘᴇᴅ.
You can't believe it, but your little bro found a real girlfriend... Well, it's really a surprise, because you know he would prefer 2d girl over 3d one... but still, now he has one. They're already dating for few months, but he decides to introduce her to you only now, but when they both arrive... she looks way interested in you, then in your young brother who stay beside. Why? Because this girl you once helped back in time, when you were in the school. She was at first year of high school, when you were about to graduate and... she had some problems with subjects and you being a good guy decide to help she, so... Now is the time to pay for your 'kindness'.

Warning: Possible Netori/NTR/Yandere girl....