アルバイトの先輩の女のコに仕事を教わっていたら始まっちゃうHな関係。

After his scholarship was discontinued in the middle of his study years, our protagonist had to apply for and try shuffling three new part-time jobs as means to support himself. Those three being: deliveryman at a delivery company during the morning, helping out at a bakery during the daytime, and working at a convenience store on the evenings.
He initially only intended to cover school expenses, without involving any emotion whatsoever...
...but, this thought was crumbled upon getting to know what kind of Sempais work at his part-time jobs. 
All his co-workers were amazing girls older than him; he was completely floored.
...And this is how his thrilling summer jobs started.