Here is the full list of all 50 Summer with Mia Season 1 achievements.
Decided on all the relationships
Chose to play without NTR when the game started
Chose to play with NTR when the game started
Got to the bathroom before Mia put the towel on
Finished the photoshoot with Mia
Finished spying on Mia in the bathroom
Finished watching Mia do yoga
Finished tricking Nathan to help you with Mia
Finished playing blackjack with Mia
Finished Mia's attempt to tease
Chose correctly when talking to Tatjana
Finished watching Mia change
Finished your first time with Mia
Finished helping someone go to bed
Finished a quickie with Mia
Finished the barbeque
Finished playing truth or dare at Sam and Emma's
Finished some much needed assistance
Finished getting through the storm
Finished helping Mia try on some clothes
Finished getting Sam to help you with Mia
Successfully "killed a spider"
Survived Mia's revenge
Finished spying while getting distracted
Finished Mia's first show
Finished a certain late night visit
Finished helping Mia with clothes shopping again
Finished a late night visit for the second time
Finished shooting your first short film
Finished getting tricked by Mia and Emma
Finished Mia's second show
Finished getting a surprise from Mia
Finished a successful massage
Finished Emma's favorite pastime
Finished Mia's third show
Finished a perfect late night visit
Finished visiting a special motel
Finished not getting caught by Mia
Finished Emma getting leverage on you
Finished Emma's "payback"
Finished having fun on your couch
Finished getting leverage on Emma
Finished going to a motel twice
Finished the "farewell" scene
Tried the cereal last
Used the Panic button once
Played all the bonus scenes
Didn't miss the password for Mia's laptop
Finished the main story
Acquired all other achievements