Here is the full list of all 15 Summer Pockets achievements.
Complete Shiroha's scenario
Complete Ao's scenario
Collect all four Celestial Beasts Islamon
Complete the Islamon Battles
Complete Tsumugi's scenario
Obtain the title, "Table Tennis God"
Participate in Islamon Battles
Use the CG Gallery
Use the Music Gallery
Complete Kamome's scenario
Complete the prologue
Play table tennis with Tenzen
Complete the ALKA scenario
Complete all scenarios
Use the Character Gallery