Yuuta, Isshiki, Shinka, Kumin, and Dekomori accompany Rikka as she heads to her grandparents' house. They take in their hospitality and swim/bake their skin at the nearby beach. It was supposed to be your clichéd high school summer vacation, but Rikka doesn't look happy to be going to her parents' house. Yuuta notices that she seems different than usual. Could he be over-thinking things?
Was there a reason the sisters live separately from their parents? Was that hidden? Unknowingly, Rikka's past is revealed.

Together with their partners in the "Far East Black Magic Napping Society of Summer," Yuuta and Rikka arrive at the "Source of Life" (the ocean). They are supposed to find a healing place there, but black haze floats around inside Rikka's soul. Worried about her, Yuuta accompanies her as she tries to find the Ethereal Horizon.

isshiki made him debut in the group, beach episode but not a totally funny was a good mix of fun and drama, dekomori suffer from the same sick of natsu from fairy tail(motion sickness) but in the end the one finished puking was isshinki, nibutane get the takanash family dog falling for her was fun too, was showed to us the takanash grandfathers(from her father) and her grandfather dont like her chuunibyu is a too much serious man, looks like isshiki have a big crush on kumin and for me looks like nibutane also start to get interesting in him too(some small jealous moments from her to him about kumin), but her tom and jerry love with dekomori still on air(they write they names on the back of each other so cut ^^), kumin is so gorgogerous on her withe dress/swimwear, and finally the mistery is revealled about rikka past, her dad died 3 years ago and her mother was not able to move from this and give both(rikka and tooka) to rikka's dad grandfather take care, rikka was unable to accept him death because she get in suprise for his death(no one have courage to told her who her father is sick and gona die soon), yuuta more and more start to accept back his oldself dark flame master mote to help rikka's quest to find the dimension of the other side horizon(talk again with her dead father) in the end us gona see again another epic fight of rikka against her sister. :D:D, amazing episode about development for me was perfect 10

In episode 5, we heard Touka say "I envy you" to Yuuta. In that episode's context, we're led to believe it's because he's so close to Rikka. After learning more about the Takanashi family, perhaps it also means she envies having a loving family living together.

Break Reality! (Shut out the real world!)
Open the Synapse! (Go into the delusional world!)
Banishment this world! (Make my real life disappear!)
Makes a bit more sense after this episode, doesn't it?

I'm very impressed on how KyoAni handled this episode. Rather than having a melodramatic turn of events, the episode focused on a wistful approach to the narrative. Often times the drama is so forced and spoon fed to the audience it becomes a huge turn off for me (Sakurasou). The ending scene with the empty lot definitely did not need any words to empathize how Rikka must have felt.

God this episode was so melancholic, but I loved every moment of it.

I feel bad for Rikka now. Not only did her father die and her mother apparently abandon her, but on top of that her grandfather doesn't accept her. No wonder she says the "Priestess" and Dekomori are the only ones to acknowledge her existance. (EDIT: And, oh yeah, returning to her childhood home to find it gone is icing on the cake of course.) Also, I think ultimatemegax is spot on about the "I envy you".

ok after rewatching the episode 5 and watch this i finally realise what really tooka wanted say when she was playing with yuuta youngest sister,:
"- i gona rise the childrens alone"(yuuta young sister who can be exactly what tooka grandfather told too and make her look too upset while playing) then she reply:
"- do not forget to let me see them once a month"(what her mother promissed but was unable to fulfill), this means the grandfather does not let her mother see them after she leave them with him, this make tooka very upste with her grandfather